Short Answer TypeOne end of a spring is kept fixed while the other end is stretched by a force as shown in the diagram.
i) Copy the diagram and mark on it the direction of the restoring force. (figure required)
ii) Name one instrument which works on the above principle.
i) F is the fixed end
ii) Spring balance works on the above principle.
Where is the center of gravity of a uniform ring situated?
The center of gravity is situated at the centre of the ring.
The position of the center of gravity of a body remains unchanged even when the body is deformed.’ State whether the statement is true or false.
False.
The centre of gravity id dependent on the shape of the object.
One Word AnswersName the form of energy which a body may possess even when it is not in motion.
Potential Energy
Short Answer TypeA force is applied on a body of mass 20 kg moving with a velocity of 40 m/s. The body attains a velocity of 50 m/s in 2 seconds. Calculate the work done by the body.
Force = 
Displacement = 
Work done = Force x Displacement
=
W = 
= 
= 9000 J
State the principle of conservation of energy.
Principle of conservation of Energy: Energy can neither be created nor destroyed. It converts energy from one form to another.
Give any two effects of a force on a non-rigid body.
Two main effects of a force on non-rigid body are:
i) It can change the state of rest or of motion of the body.
ii) It can change the size or shape of the body.
A type of single pulley is very often used as a machine even though it does not give any gain in mechanical advantage.
i) Name the type of pulley used.
ii) For what purpose is such a pulley used?
i) Single fixed pulley
ii) Single fixed pulley is used only to change the direction of the force applied.
A girl of mass 35 kg climbs up from the first floor of a building at a height 4 m above the ground to the third floor at a height 12 m above the ground. What will be the increase in her gravitational potential energy?
Gravitational potential energy at 1 st floor = mgh1
Potential energy at 3rd floor = mgh2
Increase in Potential Energy,
= 4200 – 1400
= 2800 J
With reference to their direction of action, how does a centripetal force differ from a centrifugal force.
Centripetal force is directed towards the centre of circle while centrifugal force is opposite to the centripetal force.
