Define gravitational potential energy .

Gravitational potential energy is energy stored in a mass due to its position in a gravitational field.

What happens to an object's gravitational potential energy as it rises, and as it falls?

As it rises , it gains gravitational potential energy As it falls , it loses gravitational potential energy

What value of gravitational potential energy is conventionally assigned to an object at ground level on the Earth's surface?

Zero — ground level is taken as the reference point from which gravitational potential energy is measured.

What is the shape of a graph of gravitational potential energy against height?

A straight line through the origin , since gravitational potential energy and height have a linear relationship (for constant g ).

True or False? An object only has zero gravitational potential energy when it is not moving.

False. Gravitational potential energy depends on position (height) relative to a chosen reference point, not on whether the object is moving.

Define kinetic energy .

Kinetic energy is the energy an object has due to its motion .

As an object falls, it gains kinetic energy because it is losing .......... energy.

As an object falls, it gains kinetic energy because it is losing gravitational potential energy.

True or False? If an object's speed doubles, its kinetic energy also doubles.

False. Kinetic energy is proportional to the square of velocity, so doubling the speed quadruples the kinetic energy.

A LevelPhysicsCambridge (CIE)Flashcards5. Work, Energy & PowerGravitational Potential Energy & Kinetic Energy

Gravitational Potential Energy & Kinetic Energy (Cambridge (CIE) A Level Physics): Flashcards

Exam code: 9702

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FrontGravitational Potential Energy
Define gravitational potential energy.
FrontGravitational Potential Energy
Starting from the equation for work done, $W = F s$ , derive the equation for the gravitational potential energy gained when a mass m is lifted through a height Δh.
BackGravitational Potential Energy
The force needed to lift the mass is equal to its weight, $F = m g$
The displacement is $s = Δ h$
Substituting into $W = F s$ gives $W = m g Δ h$
This work done is stored as gravitational potential energy: $Δ E_{p} = m g Δ h$
FrontGravitational Potential Energy
State the equation for the change in gravitational potential energy in a uniform gravitational field, and define each symbol.
BackGravitational Potential Energy
$Δ E_{p} = m g Δ h$
E_p = gravitational potential energy in joules (J)
m = mass in kilograms (kg)
g = gravitational field strength in newtons per kilogram (N kg^-1)
Δh = change in height in metres (m)

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Cards in this collection (14)

Define gravitational potential energy.
Gravitational potential energy is energy stored in a mass due to its position in a gravitational field.
Starting from the equation for work done, $W = F s$ , derive the equation for the gravitational potential energy gained when a mass m is lifted through a height Δh.
- The force needed to lift the mass is equal to its weight, $F = m g$
- The displacement is $s = Δ h$
- Substituting into $W = F s$ gives $W = m g Δ h$
- This work done is stored as gravitational potential energy: $Δ E_{p} = m g Δ h$
State the equation for the change in gravitational potential energy in a uniform gravitational field, and define each symbol.
$Δ E_{p} = m g Δ h$
- E_p = gravitational potential energy in joules (J)
- m = mass in kilograms (kg)
- g = gravitational field strength in newtons per kilogram (N kg^-1)
- Δh = change in height in metres (m)
What happens to an object's gravitational potential energy as it rises, and as it falls?
- As it rises, it gains gravitational potential energy
- As it falls, it loses gravitational potential energy
The equation $Δ E_{p} = m g Δ h$ is only valid for a .......... gravitational field, such as near the Earth's surface.
The equation $Δ E_{p} = m g Δ h$ is only valid for a uniform gravitational field, such as near the Earth's surface.
What value of gravitational potential energy is conventionally assigned to an object at ground level on the Earth's surface?
Zero — ground level is taken as the reference point from which gravitational potential energy is measured.
What is the shape of a graph of gravitational potential energy against height?
A straight line through the origin, since gravitational potential energy and height have a linear relationship (for constant g).
True or False?
An object only has zero gravitational potential energy when it is not moving.
False.
Gravitational potential energy depends on position (height) relative to a chosen reference point, not on whether the object is moving.
Define kinetic energy.
Kinetic energy is the energy an object has due to its motion.
State the equation for kinetic energy, and define each symbol.
$E_{k} = \frac{1}{2} m v^{2}$
- E_k = kinetic energy in joules (J)
- m = mass in kilograms (kg)
- v = velocity in metres per second (m s^-1)
Starting from $W = F s$ , $F = m a$ and $v^{2} = u^{2} + 2 a s$ for an object accelerating from rest, derive the equation for kinetic energy.
- With initial velocity u = 0, the suvat equation gives $a = \frac{v^{2}}{2 s}$
- Substituting into $F = m a$ gives $F = \frac{m v^{2}}{2 s}$
- Substituting this into $W = F s$ gives $W = \frac{1}{2} m v^{2}$
- This work done equals the kinetic energy gained: $E_{k} = \frac{1}{2} m v^{2}$
As an object falls, it gains kinetic energy because it is losing .......... energy.
As an object falls, it gains kinetic energy because it is losing gravitational potential energy.
True or False?
If an object's speed doubles, its kinetic energy also doubles.
False.
Kinetic energy is proportional to the square of velocity, so doubling the speed quadruples the kinetic energy.
How can the mass of an object be calculated if its kinetic energy and velocity are known?
Rearrange $E_{k} = \frac{1}{2} m v^{2}$ to give $m = \frac{2 E_{k}}{v^{2}}$

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