A Levels Physics

A van driver adjusts the force on a van's brakes so that the van travels at constant speed down a
hill from P to Q.
The magnitude of the change in the van's kinetic energy is AEK. The magnitude of the change in
its gravitational potential energy is AE,.
Which statement is correct?
A AE > AE,
B AE, = AE,
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C AE, > AE, > 0
D AE = 0


Choice D is correct because:

When a vehicle is moving at a constant speed, its kinetic energy remains the same. This is because kinetic energy is directly proportional to the square of the speed.

Similarly, if the van is moving at a constant speed down the hill, the gravitational potential energy is being converted into kinetic energy at an equal rate. Therefore, the change in gravitational potential energy is equal to the change in kinetic energy.

Since the kinetic energy is constant (due to constant speed), and the change in gravitational potential energy is equal to the change in kinetic energy, both changes (ΔEK and ΔEP) must be zero.

Choice A is incorrect because:

Choice A suggests that the change in kinetic energy is greater than the change in gravitational potential energy. However, this is not possible as the van is moving at a constant speed, meaning there is no change in kinetic energy.

Choice B is incorrect because:

Choice B suggests that the change in gravitational potential energy is equal to the change in kinetic energy. However, this would only be possible if the van was accelerating or decelerating, which is not the case here.

Choice C is incorrect because:

Choice C suggests that the change in gravitational potential energy is greater than the change in kinetic energy and that both are greater than zero. However, this is not possible as the van is moving at a constant speed, meaning there is no change in kinetic energy.

Work, Energy and Power | 2014 - O/N - 9702/13 | Q19