Must an object move in the direction of the force on it?

Question

Must an object move in the direction of the force on it?

Answer 1

No.  There are several instances wherein an object will not move in the direction of the force on it.

- If an object already has momentum in a direction which varies from that of the force, its motion with slow, but would continue in its original motion for a given period of time

- If an object is experiencing circular motion, often the force is directed away from the center of the orbit, and not in the direction of the orbit

- If force is exerted on an object, but the quantity of friction is greater, it will remain immobile

- If several forces are exerted on an object, such as both magnetic and physical force, the object may move in a way differeing from the direction of either force

Answer 2

No.  An object must *accelerate* in the direction of the (net) force on it, according to Newton's 2nd law:

F = m*a

Consider what happens when you hit the brakes in a car.  You're traveling forward, but by braking, the road is exerting a backwards force on the car (bringing it to a stop).  In this case, the object is moving in the opposite direction of the force on it.