(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.

1 J is the amount of work done by a force of 1 N on an object that displaces it through a distance of 1 m in the direction of the applied force.

When a force F displaces a body through a distance S in the direction of the applied force, then the work done W on the body is given by the expression:
Work done = Force × Displacement
W = F x s

Electric energy consumed by 100 W lamp
= 100 W x 2h=200 Wh = 200/1000 = 0.20 kWh
Electric energy consumed by two 60W lamps.
= 2 x 60 W x 4h = 480 Wh = 480/1000 = 0.48 kWh
Electric energy consumed by electric fan
= 50 W x 8 h = 4 00/1000 = 0.40 kWh
Total energy consumed each day
= 0.20 + 0.48 + 0.40 = 1.08 kWh = 1.08 units.

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

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 megawat t = 10⁶ watt or 1 MW = 10⁶ W
1 horse power =746 watt or 1 H.P = 746 W

We know, moment p = mv
Kinetic energy, k = 1/2mv² = (mv)²/2m = p²/2m
For same p, \(k\alpha \frac { 1 }{ m } \Rightarrow \frac { { k }_{ 1 } }{ { k }_{ 2 } } =\frac { { m }_{ 2 } }{ { m }_{ 1 } } \)
If m₁2 , then k₁>k₂
Thus, the lighter object has more kinetic energy than the heavier body.

Energy of a body is defined as its capacity or ability to do work.When a body is capable of doing more work, it is said to possess more enrgy.
Examples:
(i) When a fast moving cricket ball hits a stationary wicket, it throws away the wicket.The moving ball possess energy and hence does work on the wicket.
(ii) A hammer raised through a certain height possesses energy.When it falls on a nail placed on a piece of wood, it drives the nail into the wood.
(iii) When a child winds a toy car and does work in moving against the force of friction.
In all the above examples, the objects acquire capability of doing work through different means and these objects are said to possess energy.

m = 100 g = 1/10 kg, K.E = 20 J
K.E = 1/2 mv²
20 = 1/2 x 1/10 x v²
v² = 400 or v = 20 m/s
Momentum, p = mv = 1/10 x 20 = 2 kg m/s.

m = 10 g, p = 100 g cm/s
p = mv
v = p/m = 100/10 cm/s = 1/10 m/s
K.E.= 1/2mv² = 1/2 x 10/1000 x (1/10)²J = 5 x 10^-5J

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 

K.E.= 1/2mv².If mass is increased four times, the velocity must be reduced to half to maintain the same kinetic energy.
(K.E.= 1/2mv² = 1/2 x 4m(v/2)² = 1/2mv²)

(i) K.E. of a body is directly proportional to its mass.
\(K.E.\alpha m\)
(ii) K.E. of a body is directly proportional to the square of its velocity.
\(K.E.\alpha { v }^{ 2 }\)

(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.