6. (a)State the law of conservation of energy. (1) (b)What is the work done to increase the velocity of a car from 36 km h-1 to 72 km h-1 if the mass of the car is 1500 kg? Does the work done by the force have a negative or a positive magnitude? (2) (c) Where does an oscillating pendulum have maximum PE and KE ?(1)
Answers
Answer:
a) Whenever energy gets transformed,the total energy remains unchanged. According to this law,energy can only be converted from one form to another,it can neither be created or destroyed. The total energy before and after transformation remains same.
b) Work done to increase the velocity of a car from 36 km/h to 72 km/h if the mass of the car is 1500 kg. Hence, the work done to increase the velocity of a car from 36 km/h to 72 km/h, if the mass of the car is 1500 kg is 225000 Joule.
c) The potential energy of an oscillating pendulum is maximum at its extreme positions. In this position the pendulum bob has zero velocity. Hence, all its total energy at this position is the potential energy. The kinetic position of the pendulum is maximum at the mean position.