A pendulum is suspended from the ceiling of a car. If the car accelerates on a level ground, then the pendulum deflects opposite to the acceleration of the car. Explain.

If a pendulum is hanging from the ceiling of a car,and car accelerates forward then the pendulum tend to remain in it's original position i.e, rest position due to inertia and hence deflected in opposite direction.

and also according to Newton's second law there will be some forces :tension T along the string by the string,weight mg downward,by the earth and a pseudo force towards left.

Due to this pendulum is deflected towards left i.e, opposite to the acceleration of car with an angle of ,where a is the acceleration of car.