Laws of motion 2

Question 1

Define centripetal force

Answer 1

An external force required to make a body move along circular path with uniform speed is called centripetal force.

Question 2

Define centrifugal force

Answer 2

The outward radial force experienced by an object, when in circular motion, is called centrifugal force.

Question 3

Define pseudo force

Answer 3

A force whose source cannot be identified is called pseudo or fictitious force.

Question 4

Define angle of banking

Answer 4

The angle between the banked road and the horizontal road is called angle of banking.

Question 5

Define banking of roads.

Answer 5

The value of the maximum velocity for a vehicle to take a circular turn (without skidding) on a level road is quite low. In order that the vehicle can go round the curved track at a reasonable speed without skidding, the sufficient centripetal force is managed for it by raising the outer edge of the track a little above the inner one. It is called the banking of the circular track.

Question 6

The centripetal force at the highest point in a vertical circle is provided by the

Answer 6

Weight of the body which acts in the downward direction

Question 7

Minimum velocity the body should possess at the top, so that it can just loop the vertical circle without the slackening of the string is

Answer 7

Root gr

Question 8

The minimum velocity, which the body should possess at the bottom, so that it can just loop the vertical circle without the slackening of the string is

Answer 8

5 root gr

Question 9

The tension in the string at the lowest point in such a case =

Answer 9

is equal to six times the weight of the body.

Question 10

that angle through which the cyclist should bend will have to be greater,

Answer 10

that angle through which the cyclist should bend will have to be greater, if i) the radius of the curve is small i.e. the curve is sharper and
(ii ) the velocity of the cyclist is large.
It may be pointed out that for the same reasons, an ice skater or an aeroplane has to bend inwards, while taking a turn.

Question 11

The maximum permissible speed for the vehicle is much greater than the optimum value of the speed on a banked road. Why?

Answer 11

The maximum permissible speed for the vehicle is much greater than the optimum value of the speed on a banked road. It is because, friction between road and the tyres of the vehicle also contributes to the required centripetal force.

Question 12

Applications of centrifugal force

Answer 12

1. 1. Centrifuge. It is a device used to separate lighter particles in suspension from the more dense liquid in which they are contained. If in place of this mass of liquid, lighter particles of mass m’ (m’ < m) are present, then the centripetal force (m r w3) on the dense liquid will be greater than the centripetal force (m’ + w?) on the lighter particles.
      As a result, the lighter particles move towards the axis of the rotation under the effect of the net force (m - m’) r w2
2. Centrifugal pump. By making use of centrifugal force, it is possible to transfer. large quantities of liquid against low back pressure. Such a device is called centrifugal pump.
3. Centrifugal governors. By making use of centrifugal force, the speed of an engine can be automatically controlled.