New
New
Year 10
OCR
Higher

Calculating the energy of moving objects (E=1/2mv2)

I can calculate the energy an object has because it is moving.

New
New
Year 10
OCR
Higher

Calculating the energy of moving objects (E=1/2mv2)

I can calculate the energy an object has because it is moving.

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Lesson details

Key learning points

  1. Energy is measured in joules (J).
  2. Doubling the mass of a moving object doubles the energy it has in its kinetic store.
  3. Doubling the speed of an object increases the energy it has in its kinetic store by four times.
  4. The energy an object has in its kinetic store of energy is found using the equation E = ½ mv².

Common misconception

When calculating energy in the kinetic store, pupils often work out ½ mv and then square everything, rather than just the speed.

Scaffold calculations to show how kinetic energy is calculated, taking pupils through how to do this on their calculators without making a mistake.

Keywords

  • Work done - Work is done whenever a force makes an object move. The amount of work done is equal to the force multiplied by distance moved in the direction of the force.

  • Kinetic store - If an object is moving and has a mass, then there is energy in its kinetic store.

  • Directly proportional to - If two quantities are directly proportional, then as one increases, the other also increases at the same rate.

  • Kinetic energy - The energy an object has in its kinetic store is referred to as the object’s kinetic energy.

Do some quick calculations on calculators with pupils using mini–whiteboards to show their answers, in order to quickly identify those not squaring speed correctly on their calculators.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
Which properties of an object can be increased so it has more energy in its kinetic store?
height
Correct answer: mass
Correct answer: speed
temperature
Q2.
Why does a shopping trolley that has been pushed and then let go of come to a stop?
It runs out of energy.
Correct answer: Energy is transferred to the surroundings.
A gravitational force pushes down on it.
Q3.
What happens to the amount of work done moving a car, if the car is pushed with the same size force for three times the distance?
One third of the work.
The same amount of work.
Correct answer: Three times the work.
Nine times the work.
Q4.
In which of these situations does the applied force not do any work?
Pushing a trolley forward to speed it up.
Pushing a trolley forward against friction, to keep it at the same speed.
Correct answer: Pushing down on a trolley as it moves forwards.
Pushing on a trolley backwards to slow it down.
Q5.
How would you calculate the work done by a catapult in shooting a small ball forward?
Correct answer: Work done = force of catapult × distance over which it pushes on the ball
Work done = force of catapult ÷ distance over which the ball moves
Work done = force of catapult × mass of the ball
Work done = force of catapult ÷ mass of the ball
Q6.
A catapult does work on a small ball to fire it vertically up into the air. What is the amount of work done on the ball equal to?
Correct answer: Energy in the kinetic store as the ball leaves the catapult.
Energy in the kinetic store at its highest point.
The energy in the gravitational store when the ball leaves the catapult.
Energy in the gravitational store at its highest point.

6 Questions

Q1.
How much energy will be transferred to the kinetic store if three times the amount of work is done on kicking a football?
The same amount of energy.
Correct answer: Three times as much energy.
Nine times as much energy.
Q2.
If friction and air resistance are ignored, how much energy is dissipated by a toy car moving across a table?
All of the car's energy.
Most of the car's energy.
A tiny amount of the car's energy.
Correct answer: None of the car's energy.
Q3.
What happens to the amount of energy in the kinetic store of a ball if it is moving at two times the speed?
The amount of energy in the kinetic store does not change.
The amount of energy in the kinetic store is two times bigger.
Correct answer: The amount of energy in the kinetic store is four times bigger.
Q4.
What is kinetic energy?
The type of energy that is in the kinetic store.
The type of energy an object has because it is moving.
Correct answer: The amount of energy an object has that is in its kinetic store.
The total amount of energy that a moving object has.
Q5.
What is the kinetic energy of a discus of mass 2 kg moving at a speed of 8 m/s?
Correct Answer: 64 J, 64 Joules, 64 Joule, 64 j, 64
Q6.
What is the mass of a javelin that has a kinetic energy of 72 J and a speed of 12 m/s?
Correct Answer: 1 kg, 1 kilogram, 1, 1 kilo