(a) State the law of conservation of energy.

(b) What is the work done to increase the velocity of a car from 36 km h^-1 to 72 km hr^-1 if the mass of the car is 1500 kg ? Does the work done by the force have a negative or a positive magnitude ?

© Where does an oscillating pendulum have maximum PE and KE ?

(a) It states that energy can neither be created nor be destroyed.

(b) Given m = 1500 kg,

u = 36 km h^-1 = 10 m s^-1,

v = 72 km h^-1 = 20 m s^-1,

W = ?

Work done = Change in kinetic energy =1/2 m (v^2-u^2)=1/2 x 1500 x (20^2 -10^2) = 225000 J

The work done is positive.

© It has maximum potential energy at its extreme position and maximum kinetic energy at the mean position.