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Cambridge IGCSE Physics 0625 · Core and Extended · Topic 6
Original exam-style questions with full mark schemes. Use the filters to choose level and difficulty, and tick questions to build a printable test.
Which statement correctly describes a light-year?
| Marking point | Mark | Notes |
|---|---|---|
| A light-year is a unit of distance. It is the distance light travels through space in one year. It is not a time, despite the word 'year', and it is not a speed. | ✓ 1 | Answer A |
Answer: A
Common error: The word 'year' tempts many students to call a light-year a unit of time. It measures distance.
The Sun is a star.
Which two elements make up most of the Sun?
| Marking point | Mark | Notes |
|---|---|---|
| The Sun consists mostly of hydrogen and helium. Hydrogen nuclei fuse in its core to form helium. Oxygen and nitrogen make up most of the Earth's atmosphere. Iron and nickel make up most of the Earth's core. | ✓ 1 | Answer C |
Answer: C
Exam tip: Link the Sun's composition to its energy source: hydrogen is the fuel for fusion and helium is the product.
Which statement about the Milky Way is correct?
| Marking point | Mark | Notes |
|---|---|---|
| The Milky Way is our galaxy. It contains many billions of stars, and the Sun is one of them. The Universe contains many billions of galaxies. The Solar System is only the Sun and the objects orbiting it, and the Sun is not at the centre of the galaxy. | ✓ 1 | Answer C |
Answer: C
Common error: Do not mix up the Solar System (one star and its planets) with a galaxy (billions of stars).
Light from a distant galaxy is observed on Earth to be redshifted.
What does this mean?
| Marking point | Mark | Notes |
|---|---|---|
| Redshift is an increase in the observed wavelength of electromagnetic radiation from a source that is moving away (receding). The wavelength is shifted towards the red, long-wavelength end of the spectrum. A source moving towards us would show a decrease in wavelength. | ✓ 1 | Answer B |
Answer: B
Exam tip: Redshift has two parts: the observed wavelength increases, and the source is receding. Include both in a definition.
Astronomers studying the Solar System describe the Sun as an ordinary, mid-sized star.
Name the two elements that account for most of the mass of the Sun.
Almost all of the energy emitted by the Sun is carried by electromagnetic waves from three neighbouring regions of the spectrum. Name these three regions.
State the type of nuclear reaction that releases energy in the core of the Sun, and name the element that acts as its fuel.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| hydrogen | ✓ 1 | |
| helium | ✓ 1 | |
| Part (b) | ||
| infrared | ✓ 1 | |
| visible light (accept 'light') | ✓ 1 | |
| ultraviolet | ✓ 1 | |
| Part (c) | ||
| nuclear fusion | ✓ 1 | |
| hydrogen (nuclei fuse to form helium) | ✓ 1 | |
Common error: Fission and fusion are easily confused. Stars release energy by fusion, which joins light nuclei such as hydrogen together. Fission splits heavy nuclei.
What causes day and night on the Earth?
| Marking point | Mark | Notes |
|---|---|---|
| The Earth spins on its axis once in about 24 hours. The half of the Earth facing the Sun has day and the half facing away has night. The yearly orbit causes the seasons, not day and night. The Sun does not orbit the Earth; it only appears to move across the sky. The Moon passing in front of the Sun causes an occasional solar eclipse, not night. | ✓ 1 | Answer B |
Answer: B
Common error: Do not mix up rotation (spinning on the axis, 24 hours, day and night) with orbit (travelling around the Sun, one year).
About how long does the Moon take to complete one orbit of the Earth?
| Marking point | Mark | Notes |
|---|---|---|
| The Moon orbits the Earth in about one month (roughly 27 to 29 days), and it goes through a full cycle of phases in that time. One day is the Earth's rotation period. One year is the Earth's orbital period around the Sun. One week is roughly the time between one main phase and the next, not a full orbit. | ✓ 1 | Answer C |
Answer: C
Exam tip: Learn three periods together: Earth's rotation is about 24 hours, the Moon's orbit is about 1 month and the Earth's orbit is about 365 days.
Why does the Earth have seasons?
| Marking point | Mark | Notes |
|---|---|---|
| The Earth's axis is tilted. As the Earth orbits the Sun, each hemisphere spends part of the year tilted towards the Sun. During that time it has longer days and receives more direct sunlight, which gives summer. The Earth's orbit is nearly circular, so the change in distance is too small to cause seasons. Also, the two hemispheres have opposite seasons at the same time, which a change in distance could not explain. | ✓ 1 | Answer C |
Answer: C
Common error: Many students say summer happens because the Earth is closer to the Sun. If that were true, both hemispheres would have summer at the same time.
The average distance from the Sun to the Earth is 1.5×1011 m. The speed of light is 3.0×108 m/s.
About how long does light take to travel from the Sun to the Earth?
| Marking point | Mark | Notes |
|---|---|---|
| time = distance ÷ speed = 1.5×1011 ÷ 3.0×108 = 500 s, which is a little over 8 minutes. 50 s and 5000 s come from mistakes with the powers of ten. 4.5×1019 s comes from multiplying distance by speed instead of dividing. | ✓ 1 | Answer B |
Answer: B
Common error: Rearrange speed = distance ÷ time to get time = distance ÷ speed. Never multiply the distance by the speed.
A rover of mass 900 kg is sent to Mars. The gravitational field strength on the surface of Mars is 3.7 N/kg. The gravitational field strength on the surface of the Earth is 9.8 N/kg.
Calculate the weight of the rover on the Earth.
Calculate the weight of the rover on Mars.
Suggest why the gravitational field strength on the surface of Mars is smaller than on the surface of the Earth.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| W = mg = 900 × 9.8 | ✓ 1 | |
| = 8800 N (8820 N) | ✓ 1 | |
| Part (b) | ||
| 900 × 3.7 = 3300 N (3330 N) | ✓ 1 | |
| Part (c) | ||
| Mars has a smaller mass than the Earth | ✓ 1 | |
Common error: The rover's mass is still 900 kg on Mars. Only its weight changes, because weight depends on the gravitational field strength.
The Solar System is made up of the Sun and many objects that orbit it.
State the number of planets in the Solar System.
Name two types of object, other than planets, that orbit the Sun directly.
State the force that keeps the planets in orbit around the Sun.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| eight (8) | ✓ 1 | |
| Part (b) | ||
| One mark for each different type, from: dwarf planets (e.g. Pluto); asteroids; comets . Accept 'minor planets' as one type, but not together with dwarf planets or asteroids. Do not credit moons or natural satellites, because they orbit planets. | ✓ 2 | |
| Part (c) | ||
| the gravitational force (attraction) of the Sun on the planets / gravity | ✓ 1 | |
Common error: Moons are not a correct answer to 'orbit the Sun' because they orbit planets. For the force, magnetism and 'centripetal force' on its own do not earn the mark: name gravity as the force involved.
The Moon appears to change shape during each month, from new moon to full moon and back again.
What causes these phases?
| Marking point | Mark | Notes |
|---|---|---|
| The Sun always lights half of the Moon. As the Moon orbits the Earth, we see different amounts of that lit half, so its shape appears to change. The Earth's shadow only falls on the Moon during a lunar eclipse, which is rare. The Moon does not produce its own light; it reflects sunlight. | ✓ 1 | Answer C |
Answer: C
Common error: The phases are not caused by the Earth's shadow. That explanation describes a lunar eclipse, which can only happen at full moon.
The four planets nearest the Sun are small and rocky. The four outer planets are large and mostly made of gas.
Which statement about the formation of the Solar System explains this?
| Marking point | Mark | Notes |
|---|---|---|
| In the accretion model, the Solar System formed from a rotating cloud of gas and dust. Close to the young Sun the temperature was high, so only materials such as rock and metal could clump together. Light gases were pushed outwards and collected into the large outer planets. Option C has the effect the wrong way round: the gas ended up in the outer Solar System. | ✓ 1 | Answer B |
Answer: B
Exam tip: Link the planet types to temperature and distance from the Sun: hot near the Sun means rocky planets, cooler further out means gaseous planets.
The Earth spins on its axis and also orbits the Sun. The Earth's axis is tilted.
State the approximate time taken for
(i) one rotation of the Earth on its axis
(ii) one orbit of the Earth around the Sun.
Explain why the Sun appears to move across the sky from east to west during the day.
In June the northern hemisphere is tilted towards the Sun. Explain why the northern hemisphere is warmer in June than in December.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| (i) 24 hours / 1 day | ✓ 1 | |
| (ii) 365 days / 365¼ days / 1 year | ✓ 1 | |
| Part (b) | ||
| The Earth rotates on its axis | ✓ 1 | |
| from west to east, so the Sun appears to move in the opposite direction | ✓ 1 | |
| Part (c) | ||
| Any two from: | — | |
| days are longer, so there are more hours of sunlight; | — | |
| the Sun is higher in the sky, so its rays strike the ground more directly and more energy is received per unit area; | — | |
| sunlight passes through less atmosphere, so less energy is absorbed or scattered before reaching the ground | ✓ 2 | |
Common error: Do not explain the seasons by saying the Earth is closer to the Sun in summer. Explain them using the tilt, the length of the day and the angle of the Sun's rays.
A space probe travels directly away from Mars after taking off from its surface.
What happens to the gravitational force of Mars on the probe?
| Marking point | Mark | Notes |
|---|---|---|
| The gravitational field strength of Mars decreases as the distance from Mars increases, so the force on the probe gets smaller as the probe moves away. The force does not suddenly drop to zero, because gravity does not need an atmosphere to act. The probe's speed has no effect on the gravitational force. The mass of Mars is constant, but the field it produces is weaker further away, so the force is not constant. | ✓ 1 | Answer C |
Answer: C
Common error: Gravity does not stop at the edge of the atmosphere. It gets weaker with distance but never becomes exactly zero.
Engineers on Earth send radio signals to a rover on Mars. The distance between the Earth and Mars varies from a minimum of 5.6×1010 m to a maximum of 4.0×1011 m. Radio waves travel at 3.0×108 m/s.
Explain why the distance between the Earth and Mars varies.
Calculate the minimum time for a signal to travel from the Earth to Mars.
A signal is sent to the rover and a reply is sent straight back. Calculate the maximum time, in minutes, between sending the signal and receiving the reply.
Suggest why the rover cannot be steered around obstacles in real time by a driver on Earth.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| Both planets orbit the Sun at different distances / with different orbital periods / speeds | ✓ 1 | |
| so sometimes they are on the same side of the Sun (closest) and sometimes on opposite sides (furthest) | ✓ 1 | |
| Part (b) | ||
| t = d ÷ v = 5.6×1010 ÷ 3.0×108 | ✓ 1 | |
| = 190 s (187 s) | ✓ 1 | |
| Part (c) | ||
| t = (2 × 4.0×1011) ÷ 3.0×108 = 2670 s | ✓ 1 | |
| 2670 ÷ 60 = 44 minutes (44.4 min) | ✓ 1 | |
| Part (d) | ||
| The signals take minutes to arrive, so the rover could hit an obstacle before a command reaches it / the rover must make some decisions itself | ✓ 1 | |
Common error: A reply involves a journey there and back, so the distance must be doubled. Using only the one-way distance loses the mark.
Which statement describes the cosmic microwave background radiation (CMBR)?
| Marking point | Mark | Notes |
|---|---|---|
| The CMBR is microwave radiation that reaches us almost equally from every direction. It does not come from one source such as the Sun, the Milky Way or a supernova. Its intensity peaks at a frequency of about 160 GHz. It is radiation left over from the early Universe, and its wavelength has been stretched into the microwave region as the Universe expanded. The Sun option is wrong because the CMBR is detected day and night in all directions. The Milky Way option is wrong because the CMBR is not confined to one direction and is not produced by stars. The gamma option confuses the CMBR with high-energy radiation from violent events. | ✓ 1 | Answer C |
Answer: C
Exam tip: Link the three ideas together: microwave region, a peak frequency, and the same intensity in every direction. Together they point to an origin in the early Universe, not a nearby source.
A star stays the same size for billions of years during its stable stage.
Why is the star stable?
| Marking point | Mark | Notes |
|---|---|---|
| In a stable star, gravity pulls the material inwards. The very high temperature in the core, maintained by the fusion of hydrogen, produces an outward force. These two forces are equal and opposite, so the star neither collapses nor expands. | ✓ 1 | Answer D |
Answer: D
Exam tip: Name both forces and their directions: inward gravitational force and outward force from the high core temperature. Then state that they are balanced.
A very massive star swells to become a red supergiant.
What happens to this star next?
| Marking point | Mark | Notes |
|---|---|---|
| A red supergiant explodes as a supernova. This forms a nebula that contains hydrogen and heavier elements, with a neutron star or a black hole at its centre. A planetary nebula with a white dwarf is the end stage of a less massive star, which becomes a red giant rather than a red supergiant. | ✓ 1 | Answer A |
Answer: A
Common error: Keep the two paths separate: red giant leads to a planetary nebula and a white dwarf; red supergiant leads to a supernova and a neutron star or black hole.
A comet moves in a very elliptical orbit around the Sun.
Where is the comet's speed greatest, and why?
| Marking point | Mark | Notes |
|---|---|---|
| As the comet falls in towards the Sun, its gravitational potential energy decreases. The total energy is conserved, so its kinetic energy increases. The comet therefore moves fastest at its closest point to the Sun. Having the most potential energy far away means the comet has the least kinetic energy there, so it is slowest. Constant total energy does not mean constant speed, because energy moves between the potential and kinetic stores. | ✓ 1 | Answer B |
Answer: B
Exam tip: For elliptical orbits, use conservation of energy: closer to the Sun means less gravitational potential energy, more kinetic energy and a greater speed.
The average distances of four planets from the Sun are listed below.
Venus: 1.1×1011 m
Earth: 1.5×1011 m
Saturn: 1.4×1012 m
Neptune: 4.5×1012 m
Which planet has the lowest average orbital speed?
| Marking point | Mark | Notes |
|---|---|---|
| The Sun's gravitational field strength decreases with distance, and planets further from the Sun have lower orbital speeds. Neptune is furthest away, so it orbits the slowest. Venus is closest, so it has the highest speed, not the lowest. Being in the middle of the group gives Earth neither extreme. A planet's own mass does not decide its orbital speed. | ✓ 1 | Answer D |
Answer: D
Exam tip: Remember the trend: the further a planet is from the Sun, the weaker the Sun's field, the lower its orbital speed and the longer its orbital period.
Astronomers measure distances to stars and galaxies in light-years.
Speed of light = 3.0 × 108 m/s.
1 year = 3.15 × 107 s.
State what is meant by a light-year.
Show that one light-year is approximately 9.5 × 1015 m.
A nearby star is 4.2 light-years from the Earth. State how long ago the light now reaching the Earth left this star.
The diameter of the Milky Way is about 100 000 light-years. Calculate this diameter in metres.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| the distance travelled by light (in a vacuum) in one year | ✓ 1 | |
| Part (b) | ||
| distance = speed × time = 3.0 × 108 × 3.15 × 107 | ✓ 1 | |
| = 9.45 × 1015 m ≈ 9.5 × 1015 m | ✓ 1 | |
| Part (c) | ||
| 4.2 years ago | ✓ 1 | |
| Part (d) | ||
| 100 000 × 9.5 × 1015 (or 100 000 × 9.45 × 1015) | ✓ 1 | |
| = 9.5 × 1020 m (accept 9.45 × 1020 m) | ✓ 1 | |
Exam tip: In a 'show that' question, write out the full calculation and give the answer to more significant figures than the value you were given.
For a distant galaxy, the Hubble constant is given by H0 = v/d. Here v is the speed at which the galaxy recedes and d is its distance from the Earth.
Which is the unit of H0?
| Marking point | Mark | Notes |
|---|---|---|
| H0 = v/d, so its unit is (m/s) ÷ m. The metres cancel, leaving 1/s, or per second. Its value is about 2.2 × 10−18 /s. m/s ignores the division by distance. s is the unit of 1/H0, not of H0. m/s2 comes from dividing a speed by a time instead of by a distance. | ✓ 1 | Answer D |
Answer: D
Exam tip: Find a derived unit by putting the units into the defining equation and cancelling.
Stars form, change and eventually die. This question is about a star with a mass similar to the Sun's.
Describe how a star is formed.
Explain why the star then remains stable for a very long time.
Describe what happens to this star when most of the hydrogen in its core has been used up.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| a cloud of gas and dust in space (nebula) is pulled together / collapses under gravity | ✓ 1 | |
| forming a protostar, which heats up until the temperature is high enough for nuclear fusion of hydrogen to begin | ✓ 1 | |
| Part (b) | ||
| the inward pull of gravity is balanced by an outward force / pressure, so the star stays the same size (equilibrium) | ✓ 1 | |
| the outward force / pressure comes from the very hot core (gas or radiation pressure), kept hot by energy released in hydrogen fusion | ✓ 1 | |
| Part (c) | ||
| it expands (and its surface cools) to become a red giant | ✓ 1 | |
| its outer layers are thrown off as a planetary nebula, leaving a (hot, dense) white dwarf at the centre | ✓ 1 | |
Exam tip: Check the mass of the star in the question. A star like the Sun becomes a red giant, not a red supergiant, and does not explode as a supernova.
An astronomer studies the light from a distant galaxy. She finds that the galaxy is moving away from the Earth at 2.1 × 107 m/s.
Hubble constant H0 = 2.2 × 10−18 per second.
1 light-year = 9.5 × 1015 m.
State what is meant by redshift.
Calculate the distance of the galaxy from the Earth in metres.
Convert your answer to part (b) into light-years.
Astronomers can also find the distance to a far galaxy without using redshift. State what is measured to do this.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| an increase in the observed wavelength of electromagnetic radiation (light) from a source that is moving away / receding (accept: spectral lines shifted towards the red / longer-wavelength end) | ✓ 1 | |
| Part (b) | ||
| d = v / H0 = 2.1 × 107 / 2.2 × 10−18 | ✓ 1 | |
| = 9.5 × 1024 m | ✓ 1 | |
| Part (c) | ||
| 9.5 × 1024 / 9.5 × 1015 | ✓ 1 | |
| = 1.0 × 109 light-years (allow error carried forward from (b)) | ✓ 1 | |
| Part (d) | ||
| the (apparent) brightness of a supernova in that galaxy (accept: the brightness of another standard candle of known luminosity, e.g. a Cepheid variable star) | ✓ 1 | |
Exam tip: Rearrange H₀ = v/d to d = v/H₀ before you substitute the values. This avoids errors with the powers of ten.
Venus orbits the Sun with an average orbital radius of 1.08×1011 m. Its orbital period is 225 days.
Convert the orbital period of Venus into seconds.
Calculate the average orbital speed of Venus.
The Earth's average orbital speed is 3.0×104 m/s. Explain why the orbital speed of Venus is greater than that of the Earth.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| 225 × 24 × 3600 = 1.94×107 s | ✓ 1 | |
| Part (b) | ||
| v = 2πr/T = (2π × 1.08×1011) ÷ 1.94×107 | ✓ 1 | |
| = 3.5×104 m/s | ✓ 1 | |
| Part (c) | ||
| Venus is closer to the Sun (it has a smaller orbital radius) than the Earth, so the Sun's gravitational field strength is greater at its orbit | ✓ 1 | |
| The greater gravitational pull (per kg) means Venus must travel faster to stay in its circular orbit around the Sun | ✓ 1 | |
Exam tip: In orbital-speed questions, write v = 2πr/T first, substitute the values with the period in seconds, and only then work out the answer.
According to the Big Bang theory, the Universe began as an extremely small, extremely hot region and has been expanding ever since. Two kinds of observation support this theory.
Describe what is observed in the light from distant galaxies, and state what this shows about the galaxies.
Describe the cosmic microwave background radiation (CMBR).
Explain how the CMBR supports the Big Bang theory.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| the light is redshifted: observed wavelengths are longer (frequencies lower) than for the same source measured on Earth | ✓ 1 | |
| so the galaxies are moving away from us; more distant galaxies recede faster / the Universe is expanding | ✓ 1 | |
| Part (b) | ||
| it is electromagnetic radiation in the microwave region; accept 'of a particular frequency' or 'a range of frequencies with a peak' | ✓ 1 | |
| it reaches us from every direction / from all points in space, with almost the same intensity | ✓ 1 | |
| Part (c) | ||
| it is radiation left over from the early Universe, emitted when the Universe was very hot and dense, so it originally had a much shorter wavelength | ✓ 1 | |
| as the Universe expanded, this wavelength was stretched (redshifted) into the microwave region | ✓ 1 | |
Common error: Writing only 'the Universe is expanding' does not describe the evidence. State what is actually observed: longer wavelengths in light from distant galaxies, and microwave radiation arriving from all directions.
Light from two distant galaxies, X and Y, is analysed. Light from galaxy X shows a greater redshift than light from galaxy Y.
Which statement is correct?
| Marking point | Mark | Notes |
|---|---|---|
| A greater redshift means a greater recession speed, so X is moving away faster. The speed of a galaxy is proportional to its distance (v = H0d), so a faster galaxy is also further away. Both galaxies are redshifted, so both are moving away. | ✓ 1 | Answer B |
Answer: B
Common error: Do not assume a nearer object must be moving faster. In the expanding Universe, more distant galaxies recede faster.
A galaxy is 2.0 × 108 light-years from the Earth.
1 light-year = 9.5 × 1015 m.
The Hubble constant H0 = 2.2 × 10−18 per second.
At what speed is the galaxy moving away from the Earth?
| Marking point | Mark | Notes |
|---|---|---|
| First convert the distance to metres: d = 2.0 × 108 × 9.5 × 1015 = 1.9 × 1024 m. Then v = H0d = 2.2 × 10−18 × 1.9 × 1024 = 4.2 × 106 m/s. Each wrong option comes from a specific mistake: • 4.4 × 10−10 m/s: the distance was not converted from light-years to metres. • 0.13 m/s: the speed of light was wrongly used as the light-year conversion factor. • 8.6 × 1041 m/s: the distance was divided by H0 instead of multiplied. | ✓ 1 | Answer C |
Answer: C
Common error: Convert distances to metres before using H₀ in per second. Otherwise the speed will not come out in m/s.
Mars orbits the Sun at an average radius of 2.28×1011 m. Its orbital period is 687 days.
What is the average orbital speed of Mars?
| Marking point | Mark | Notes |
|---|---|---|
| First convert the period to seconds: T = 687 × 24 × 3600 = 5.94×107 s. Then v = 2πr/T = (2π × 2.28×1011) ÷ 5.94×107 = 2.4×104 m/s. Leaving out the 2π gives 3.8×103 m/s. Using πr (half the circumference) gives 1.2×104 m/s. Leaving T in days gives 2.1×109 m/s. | ✓ 1 | Answer C |
Answer: C
Common error: Always convert the period into seconds before using v = 2πr/T if you want the speed in m/s.
A comet of mass 2.0×1014 kg orbits the Sun. At its furthest point from the Sun its speed is 900 m/s. As it travels from its furthest point to its closest point, it loses 4.5×1022 J of gravitational potential energy. Assume that no energy is lost.
Describe the shape of the comet's orbit and the position of the Sun within it.
State the energy change as the comet moves towards the Sun.
Calculate the kinetic energy of the comet at its furthest point from the Sun.
Calculate the speed of the comet at its closest point to the Sun.
| Marking point | Mark | Notes |
|---|---|---|
| Part (a) | ||
| The orbit is an ellipse / very elongated | ✓ 1 | |
| The Sun is not at the centre of the orbit; it is near one end (at one focus) | ✓ 1 | |
| Part (b) | ||
| Gravitational potential energy decreases | ✓ 1 | |
| and is converted into kinetic energy, which increases | ✓ 1 | |
| Part (c) | ||
| KE = ½mv2 = 0.5 × 2.0×1014 × 9002 | ✓ 1 | |
| = 8.1×1019 J | ✓ 1 | |
| Part (d) | ||
| KE at closest point = 8.1×1019 + 4.5×1022 = 4.5×1022 J (4.508×1022 J) | ✓ 1 | |
| v = √(2 × KE ÷ m) = √(2 × 4.508×1022 ÷ 2.0×1014) | ✓ 1 | |
| = 2.1×104 m/s | ✓ 1 | |
Exam tip: Add the starting kinetic energy to the loss of potential energy to find the final kinetic energy. Then rearrange KE = ½mv² to find v.
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