Work and Energy Test - 6

Force is the product of mass and acceleration due to gravity.
Mass = 2m and acceleration due to gravity =g m/s². 
Force = 2 × m × g = 2mg.

Work done = W = F x S cos θ
( cos 900 = 0) 
So, W = 0
so, Q =45⁰.

Work is said to be done when there is a displacement of the body with respect to moving body. No work is done when a camel is carrying a load on its back. But work is done when a sailboat is moving due to wind energy. So, statement B is true statement.

In general, work represents any physical or mental activity. But work has precise meaning in physics. Work is said be done when a net force acts on a body and the body undergoes displacement.  So statement  A is false .
Work done by a force is positive if the applied force has a component in the direction of the displacement. So, statement B is true.

The simplest formula for mechanical work (in Physics) is W=Fs.
Here, the force is constant and parallel to displacement and the body moves in a steady direction. W is work, F is force and s is displacement. The result is in Joules.

No work is done in reading a book, pulling wall of house and walking on a level road with book on his head as there is no change in the position of object on which force is applied. Stretching string causes displacement after applying force, so it is a work.

(1) Work is defined as a force acting upon an object to cause a displacement . Unit of work is Joule.
(2) Rate of doing work is called power. The SI unit of power is watt.
(3) Energy is the capacity of doing work. Large quantity of energy is expressed in kilo watt hour and is written as kWh.
(4) Unit of force is Newton.