Physics [1 Mark Question Answer]

A balance becomes faulty, if the lenghts of its arms are unequal or the weughts of both the pans are not same.

Mechanical advantage (M.A.): The ratio of the load to the effort is called the mechanical advantage of the machine.

Lever: A lever is a rigid, straight or bent bar which is capable of turning about a fixed axis.

Electric iron

Solar cell

Dry cell

Candle flame

Electric bell

P.E (Wound spring) to K.E. (motion)

P.E (stone at the top of cloff) → K.E (falling stone) → P.E (stone at ground).

Chemical energy (chemical reaction) → Heat energy (burning)

Electrical energy (electric current) → light energy + Heat energy (bulb).

P.E (water stored in the dam) → K.E (falling water) → Electrical energy (Generators of turbine form electrical energy).

By keeping the legs apart, the base of the body broadens, thus the C.G. lowers and the body attains a more stable equilibrium.

To increase the stability of a body, its base should be made broad and heavy, and the centre of gravity of the body should be lowered. 

A body is said to be in equilibrium under the action of a number of forces, if the forces are not able to produce any change in the state of rest or of uniform motion or uniform rotation.

The point through which the resultant of the weights of all the particles of the body acts is called its centre of gravity 

A larger diameter provides a greater torque (= force x perpendicular distance); hence, it is easier to turn a steering wheel of a large diameter than that of a small diameter.

No, the moment of force is a vector quantity. 

The physical quantity is 'torque'.

Yes, the centre of gravity of a body can be outside it. The CG of a uniform ring is at its centre, a point which is not on the body. 

The centre of gravity of a uniform ring is situated at the centre of the ring.

The point through which the resultant of the weights of all the particles of the body acts is called its centre of gravity

Yes, if the body is not in motion; it has zero kinetic energy 

Energy is a scalar quantity. 

'Energy' is the body's ability to do work. 

Work

SI unit of energy is 'joule'. 

P.E. is a scalar quantity. 

Examples of kinetic energy:
(i) Air in motion has kinetic energy.
(ii) A swinging pendulum

The work done in winding a clock spring is stored as P.E. in the spring. This P.E. is then used to run the hands of the clock.

Potential energy 

The energy spent by the heart in pumping blood through the body is 1 J per beat. 

P.E of a body lying on a floor is zero. 

Examples of potential energy:
(i) Water stored at a height in a reservoir.
(ii) A stretched spring.

The energy possessed by a body by virtue of its position, shape or change of configuration is called potential energy. 

A ball at lying at rest on the floor possesses zero kinetic energy. 

The energy possessed by a body by virtue of its motion is called kinetic energy. 

The car should be moving faster because the mass of the car is less than that of the bus.

Flowing water possesses kinetic energy. 

A moving bullet possesses kinetic energy 

A D.C. motor converts electrical energy into mechanical energy.

A dry cell converts chemical energy into electrical energy. 

Energy is the capacity or ability of a body to do work or energy is stored work.

No, we cannot destroy energy associated with a body. 

Energy is a scalar quantity. 

No, total energy of a body does not remain constant but the total energy of a closed system remains constant e.g. universe. 

When we rub our hands, mechanical energy is converted into heat energy.

This heat energy comes from the mechanical energy.