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# Pendulum in car - Please help me!?

A 0.6 kg sphere hangs on a string from the ceiling of an automobile. The car has a constant horizontal acceleration and the string is displaced an angle q = 65.2° from the vertical. To a person sitting inside the car, it appears that the sphere is motionless (the angle between the sphere and the vertical is constant).

What is the magnitude of the acceleration of the car?

/a/= ? m/s^2

### 3 Answers

- 1 decade agoFavorite Answer
The tension (force) on the string is completely balanced by the weight of the sphere (vertical component of force) and the force on the sphere associated with the horizontal acceleration of the car-pendulum system (all add up to zero, calculated from frame of reference inside the car).

weight = (0.6 kg)* g = cos (q)* tension, together with

F(horiz) = (0.6 kg) * (acceleration of car) = sin (q)* tension

Solve for acceleration.

- 1 decade ago
What you are asking is a very simple question in dynamics. I would advice you to try solving more problems in dynamics from the book problems in genral physics by I.E.Irodov or From Halliday&Resnic.