Reason: Centripetal force is essential to keep a particle in circular motion.
Q. 2. Assertion: The turning effect on the body about an axis is due to the moment of force (or torque) applied on the body.
Reason: The SI unit of moment of force is N-m.
Q. 3. Assertion: Equilibrium means either the body is at rest (static equilibrium) or in uniform motion (dynamic equilibrium).
Reason: When the resultant force is zero or there is no unbalanced force, the body is said to be in equilibrium.
Q. 4. Assertion: The moon revolving around the Earth is in dynamic equilibrium.
Reason: For a body to be in equilibrium the resultant of all the forces acting on the body should be positive.
Q. 5. Assertion: Centripetal and centrifugal forces don't act at the same
time. Reason: In circular motion, the centripetal and centrifugal force acting in opposite direction balances each other.
Q2. Define Moment of force and state its S.I unit.
Q3. State two factors affecting the turning effect of a force.
Q4. The moment of force of 20N about a fixed point O is 10 Nm . Calculate the distance of the point O from the line of action of force.
Q5. Distinguish between Energy and Power.
Q6. A pump is used to lift 600kg of water from a depth of 75 km in 10 secs . Calculate the work done by the pump.
Q7 . Distinguish between potential and kinetic Energy.
Q8. Find kinetic Energy of a body of mass 5kg moving with uniform velocity 10 ms-1.
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