Question

@Abhisar
A mass is attached at the end of a string which hangs from roof of a car. Describe and explain the position of the mass as seen by a passenger in the car when i) the car travels along a straight horizontal road with an acceleration which increases uniformly. ii) the car travels with constant speed of 60km/h in a horizontal circular track of radius 50 m.

Answer 1

So we were talking about Newton's First law. Which says that a body in rest will remain in rest unless until a net force is applied o it.

Answer 2

Inertia,right?

Answer 3

Yes...inertia
Considering the case #1

When the car is at rest the ball hangs vertically downwards as shown in the figure. When the car starts moving with an acceleration the whole body of the car moves forward but the ball which is hanging from the roof (and is not in direct contact with the car) stays back at its initial position since no force is applied on it immediately. For a passenger who is sitting in the car (frame of reference for him is the car itself for him) it appears that the ball has moved backwards. Now as the acceleration keeps increasing the balls keep moving backwards for him

Answer 4

Getting it ?

Answer 5

yes...get it...

Answer 6

Case #2
In this case the car moves with a circular track and in circular motion despite of constant speed there is always a centripetal force acting towards the center. Again since the ball hanging from the roof do not experience any force immediately (because it is not in direct contact with the car) it stays back at its initial position. due to this it appears that the ball has shifted sideways.

`Try to imagine the situation when we are sitting in a car and at a sudden turn it feels like we have been thrown to the opposide side of the turn`

Answer 7

Getting it ?

Answer 8

Not very understand...

Answer 9

Hmm..what part is giving u trouble ?

Answer 10

It's the same thing only this time the ball will appear to move sideways instead of bakwards

Answer 11

why the centripetal force always act towards the centre?

Answer 12

Because it's kinda binding force which enables a body to perform circular force.

Answer 13

*circular motion

Answer 14

O....ok...

Answer 15

Is everything clear ?

Answer 16

Ya...Can u simply explain me about circular motion...i'm not understand when teacher r teaching...

Answer 17

???

Answer 18

http://hyperphysics.phy-astr.gsu.edu/hbase/circ.html

Answer 19

ok...thanks for your help...

Answer 20

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