What is the equation for kinetic energy?
Give SI units for all quantities involved.
½ m v2
½ x Mass x (Velocity)²
Energy (J), Mass(kg), Velocity(m/s)
www.pmt.
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What is the equation for elastic potential
energy? Give SI units for all quantities
involved.
½ k x2
½ x Spring Constant x (Extension)²
Energy (J), Spring Constant (N/m), Extension(m)
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What is the equation for gravity potential
energy? Give SI units for all quantities
involved.
mgh
Mass x Gravitational Field Strength x Height
Energy (J), Mass(kg), Gravitational Field Strength (N/kg),
Height (m)
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Define the ‘Specific Heat Capacity’ of a
substance.
The amount of energy needed to raise
the temperature of 1 kilogram of a
substance by 1 degree Celsius.
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State the units for Specific Heat
Capacity.
J/°C/kg
Joules/Degree Celsius/Kilogram
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What is the definition of ‘Power’?
The rate at which energy is transferred
(or rate at which work is done).
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State two equations for power. Give SI
units for all quantities involved.
power = energy transferred/time
power = work done/time
Energy (J), Work Done (J), Time (s)
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What is the unit of power?
Watt (W)
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Two motors lift the same mass through
the same height. Motor A does this in
half the time of Motor B. Which
dissipates the most power?
Motor A.
The energy transferred is the same but
the time taken is less (P=E/t).
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Describe the energy changes involved
when a ball is thrown upwards and then
returns to its starting position. Ignore air
resistance.
● Upwards: KE is converted to GPE
● Peak: Maximum GPE, zero KE
● Downwards: GPE is converted to KE
KE (Kinetic Energy), GPE (Gravitational Potential Energy)
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Describe the energy transfers for a
bungee jumper.
● When falling, the GPE is converted to KE of
jumper
● As the cord tightens, KE is converted and
stored as Elastic Potential Energy (EPE)
● At lowest point, the jumper’s initial GPE
equals the EPE stored in the cord
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Explain why a bungee jumper slows
down once the cord begins to stretch.
● Kinetic energy decreases since it is
converted to elastic potential energy
● Since KE is proportional to (velocity)²,
as KE decreases, so does velocity.
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