State whether the following statement is true or false:
Kilowatt hour $(kWh)$ is the unit of power.

$(a)$ Define one watt.
$(b)$ $A$ lamp consumes $1000 \ J$ of electrical energy in $10 \ s$. What is its power?

$A$ ball is dropped from a height of $10\, m$. If the energy of the ball reduces by $40\%$ after striking the ground,how much high can the ball bounce back (in $,m$)? $(g = 10\, m \,s^{-2})$

Justify,giving proper reasoning,whether the work done in the following case is positive or negative: Work done by gravitational force when a bucket is pulled upwards.

When a stone of mass $m$ falls through a vertical height $d$,the decrease in the gravitational potential energy is:

Justify,giving proper reasoning,whether the work done in the following case is positive or negative: Work done by friction on a body sliding down an inclined plane.