physics (forces)

Question

A non-zero net force acting on an object can have which of the following effects on the object?

Question 1 options:

	the velocity can increase
	the velocity can decrease
	the velocity of the object can change direction
	all of the above

Answer 1

Consider an object with a non-zero velocity,

and consider a force acting on the object.

Both the velocity and force are vectors, which could be at an arbitrary angle to each other.

The force can be always decomposed into a vector sum of two components:

a force parallel with velocity, and

a force perpendicular to velocity.

If the parallel component is non-zero, and in the direction same as velocity,

then it will cause increase in the velocity magnitude.

If the parallel component is non-zero, and in the direction opposite to velocity,

then it will cause decrease in the velocity magnitude.

If the perpendicular component is non-zero,

then it will cause change in the velocity direction.