(a) Heat energy produced in the engine into K.E. of the car.
(b) Electric energy into potential energy
(c) Electric energy into mechanical energy
(d) P.E. into K.E.
(e) Electrical energy into heat and light.
(f) Electrical energy into sound energy.
(g) Chemical energy into heat energy and light.

Work is said to be done whenever a force a acts on a body moves in the direction of the force.
Two conditions need to be satisfied for work to be done.These are as follows:
(i) A force should act on the body.
(ii) The body must be displaced in the direction of the applied force.
If either of the above two conditions is not satisfied, then work is not done.
Examples: We give below some situations from daily life in which work is done.
(i) Push a pebble lying on a surface.The pebble moves through some distance.Here we apply a force on the pebble and the pebble gets displaced.So, we have done work on the pebble.
(ii) We apply a force to lift a book through a height.The book rises up.We have done work in moving up the book.
(iii) A bullock is pulling a cart.The cart moves.There is a force on the cart and the cart has moved.The bullock has done work on the cart.

A flying bird has potential energy due to its height h above the ground.This energy is
E_p= mgh
Due to its velocity v, the flying bird has a kinetic energy given by
E_k= 1/2mv².

Let the mass of each body be m.
K.E. of the first body, K₁ = 1/2m(2v)²
K.E. of the second body, K₂ = 1/2m(3v)²
Ratio of the kinetic energies=K₁/K₂ = 1/2m.4v² /1/2m.9v² = 4/9 = 4:9 

An object that possesses energy can exert a force on another object.When this happens, energy is transferred from the former to the latter.The second object may move as it receives energy and therefore do some work.Thus, the first object has a capacity to do work.This implies that any object that possesses energy can do work.

Here, Force(F) = 140N, Displacement (s) = 15m
Work done, W = Fs = 140 N x 15 m = 2100 J

Zero.
This is because the component of the force acting on a body in the direction of its displacement is zero in this case.Moreover,
\(W=F\ s\ cos\ 90°=0\)

Here, m = 40 kg, g = 10 ms^-2, h = 5m
Potential energy of the object at a height of 5m,
E_p = mgh =40 x 10 x 5= 2000J
When the object is half-way down, let its velocity be v.Then
v²- u² = 2gs
v² - 0² = 2 x 10 x 2.5 or v² = 50
Kinetic energy of the object, E_k=1/2 x 40 x 50 = 1000 J

The SI unit of power is watt(W). The power of an agent is one watt if it does work at the rate of 1 joule per second.
1 watt = 1joule/1 second. or 1W = 1 Js^-1
We can also say that power is 1 watt when the rate of consumption of energy is 1   Js^-1 .
Bigger units of power are kilowatt, megawatt, and horsepower.
1 kilowatt =1000 watt or 1 kW = 1000 W
1 megawatt = 10⁶ watt or 1 MW = 10⁶ W
1 horse power =746 watt or 1 H.P = 746 W

Here m = 25 kg, h = 10m, g = 10m/s²
(a) Work done = mgh =25 x 10 x 10J = 2500J
(b) Gravitational P.E.= Work done  =2500J
(c) Gravitational P.E. at a height of 30m = 25 x 30 x 10J = 7500J
P.E. at 30 m height/P.E. at 10m height = 7500J/2500J = 3
Thus, P.E. increases by 3 times.
(d) K.E. of the body will be maximum just before the body strikes the ground.

Here m = 1000 kg, u=30 m/s, v = 0, s = 50 m
v² - u² = 2as
0-30² = 2a.50 or a = -900/100 = -9 m/s²
Deceleration=  9m/s²
decelerating force, F = ma =1000 x 9 = 9000 N
Work done by the brakes, W = F.s = 9000 x 50J = 450000J

Kinetic energy is the energy possessed by a body by the virtue of its motion. Every moving object possesses kinetic energy. A body uses kinetic energy to do work. Kinetic energy of hammer is used in driving a nail into a log of wood, kinetic energy of air is used to run wind mills, etc.

(i) First the battery converts chemical energy into electrical energy. Then the bulb converts this electrical energy into heat and light.
(ii) Here, m = 500 kg, v = 0 and
u = 36 kmh^-1  = \(\frac{36\times 1000}{3600}\) = 10 ms^-1
\(\therefore\) Work done = Change in kinetic energy
= \(\frac{1}{2}m(v^2-u^2)=\frac{1}{2}\times 500(0-10^2)\)
= \(\frac{1}{2}\times 500\times 100\) = - 25000 Js^-1
So, it is negative because work is done to stop the car.