Speed (m/s) = distance travelled (m) / time taken (s)
Work done (J) = Force (N) / Distance (M)
KE = 1/2 m v(squared)
GPE = mgh
Average acceleration = change in velocity / time taken
'Work done' questions
1. Calculate the work done if the force is 10N and the distance is 10m.
2. Calculate the work done if the force is 17.5N and the distance is 15m.
3. Calculate the work done if a man walks 100m and the force on him is 57N.
4. What is the work done to move three books a distance of 95m is each book has a force of 10N?
5. What is the work done to move five books, each with a force of 5N, up a 200m high hill?
Answers on next slide.
'Work done' answers
KE = 1/2 M V(squared)
If the mass of an object is increased, the kinetic energy increases.
If the velocity is doubled, the kinetic energy is quadrupled.
To decrease the kinetic energy of an object, you can:
- Decrease the mass
- Decrease the velocity
Statistically, the relationship between kinetic energy and velocity can be described as y=x(squared).
GPE = mgh
If you increase the height or mass of an object, the gravitational potential energy also increases.
To decrease the gravitational potential energy of an object:
- Decrease its mass
- Decrease its height
Statistically, the relationship between gravitational potential energy and height is proportional.
When a rollercoaster is at the top of the ride, on a flat surface:
- Maximum height
- Maximum gravitational potential energy
- No velocity
- No kinetic energy
- All energy is stored as gravitational potential energy
As it goes down the ramp:
- Kinetic energy is increasing
- Gravitational potential energy is decreasing
- Energy is being transferred from one form to another
At the bottom of the ride:
- No height
- No gravitational potential energy
- Maximum kinetic energy
- Maximum velocity
- All energy is transferred into kinetic energy
Gravitational Vs Kinetic energy
Only gravitational potential energy:
Involved in gravity and height
Lost as an object falls
Is stored energy
Only kinetic energy:
Involved in speed
Gained as an object falls
Is active energy
Energy is measured in joules
Exclusing efficiency, they equal each other
1. A car is pushed 30m with a force of 400N. How much work is done?
2. How much gravitational potential energy is gained by lifting a 300N suitcase a height of 1m?
3. A bowling ball has a mass of 4kg and is moving at 8m/s. How much kinetic energy does it have?
4. A trolley is pushed with a force of 6N over a distance of 5m. How much work is done?
5. If you weigh 40kg, your weight is roughly 400N. How much gravitational potential energy do you gain to move a vertical height of 2.5m?
6. Which has the most kinetic energy: a car of mass 500kg at 20m/s or a car of mass 1000kg at 10m/s?
Answers on next slide
6. They are the same.