When a body slides against a rough horizontal surface, the work done by friction is………..
a) positive
b) negative
c) zero
d) constant
Explanation: If a force acting on a body has a component in the opposite direction of displacement, the work done is negative, when a body slides against a rough horizontal surface, its displacement is opposite to that of the force of friction. Hence works done by the friction is negative.
For a body moving in a circular path, the work done by the centripetal force is…………..
a) positive
b) negative
c) zero
d) constant
Explanation: For a body moving in a circular path, the centripetal force and the displacement are perpendicular to each other. So the work done by the centripetal force is zero.
A person pulls a suitcase through the airport at an angle of 450. The tension in the rope is 20N. How much work does the tension do if the suitcase is pulled 100m?
a) 1300J
b) 1400J
c) 1500J
d) 1600J
Explanation: W = Fcos θ x s
Energy and its Forms:
……….is the capacity of a body to do work.
a) potential
b) force
c) power
d) energy
The S.I unit of energy is…………….
a) calorie
b) horse power
c) watt
d) joule
