P4.4

Question 1

1. What is the energy of a moving object called?

Answer 1

-its kinetic energy

Question 2

2. What is gravitational potential energy (G.P.E.)?

Answer 2

-the energy stored in the object when you raise it to a height against the force of gravity

Question 3

2. What happens to an objects gravitational potential energy as it is raised and as it falls?

Answer 3

• raised= G.P.E. increases

- falls= G.P.E. decreases

Question 4

3. What happens when a force moves an object?

Answer 4

• it does work

- energy is transferred into the object

Question 5

4. What is the equation for work done by a force? (And units)

Answer 5

work done by a force (joules, J) = force (newtons, N) × distance moved in the direction of the force (metres, m)

Question 6

5. What happens when work is done ON an object?

Answer 6

-energy is transferred TO the object

Question 7

5. What happens when work is done BY an object?

Answer 7

-energy is transferred FROM the object to something else

Question 8

5. What is the relationship between amount of energy transferred and work done? What are they both measured in?

Answer 8

-amount of energy transferred (joules, J) = work done (joules, J)

Question 9

6. What happens when an object is lifted to a higher position above the ground?

Answer 9

• work is done by the lifting force

- this increases the gravitational potential energy

Question 10

7. What is the equation for change in gravitational potential energy? (And units)

Answer 10

change in gravitational potential energy (joules, J) = weight (newtons, N) × vertical height

Question 11

8. What happens when a force acting on an object makes its velocity increase?

Answer 11

-the force does work on the object and this results in an increase in its kinetic energy

Question 12

9. What increases an objects kinetic energy?

Answer 12

-the greater the mass of an object and the faster it is moving, the greater its kinetic energy

Question 13

10. What is the equation for kinetic energy? (And units)

Answer 13

kinetic energy (joules, J) = ½ × mass (kilograms, kg) × [velocity]2 ([metres per second]2, [m/s]2)

Question 14

11. What is the relationship between an object’s kinetic energy and work done?

Answer 14

-if friction and air resistance can be ignored, an object’s kinetic energy changes by an amount equal to the work done on it by an applied force

Question 15

12. What affects the relationship between an object’s kinetic energy and work done?

Answer 15

-air resistance or friction will cause the gain in an object’s kinetic energy to be less than the work done on it by an applied force in the direction of motion, because some energy is dissipated through heating

Question 16

13. What happens to energy in events and processes?

Answer 16

-energy is always conserved in any event or process