[Kinetic and Potential Energies]

Question 1

5. Kinetic Energy

Answer 1

EK. Energy associated with an object as a result of its motion.
EK = 1⁄2 m v2. EK =kinetic energy; m = mass; v = speed.

Question 2

6. Gravitational Potential Energy

Answer 2

EP. The capacity for doing work as a result of an object’s position in a gravitational field. ‘Potential’ refers to ‘hidden’ or ‘stored’. In a uniform gravitational field of strength, g: EP = m g h = W h.
EP = gravitational potential energy; m = mass; g = gravitational field strength; h = height; W = weight.

Question 3

7. Uniform Gravity Field

Answer 3

Gravitational field has a constant gravitational field strength, g. For example, g = 9.81 ms-2 or Nkg-1. Field lines are parallel. Objects have a weight equal to W = m g and acceleration due to gravity is g.

Question 4

8. Exchange of GPE and KE

Answer 4

From the principle of conservation of energy and assuming no energy is transferred to heat due to friction: Maximum EK equals Maximum EP or the loss of one equals the gain of the other.
E.g. For a falling object: m g h = 1⁄2 m v2; so maximum speed can be worked out using v = √ 2 g h.
If energy is lost due to friction, the energy lost is equal to work done, W = F d. E.g.For a falling object :mgh=1⁄2mv2 +Fd.