Question

1. In many cases, when we are solving problems we can assume the Net Force on an object in question is zero.
Which of the following is an example where this is NOT the case.

	A.	An object is stated to be moving at a constant speed in a circle.
	B.	An object is stated to be at rest.
	C.	An object is stated to have zero acceleration.
	D.	An object is stated to be moving at a constant velocity.

2. When using the formula : F = ma   

The mass must be converted to kilograms in order for the force to have the correct units of Newtons.

True

False

3. When we are solving problems involving multiple forces on an object, the normal force will always be equal and opposite to the object's weight.

True

False

Answer 1

1. Answer is A

An object is stated to be moving at a constant speed in a circle.

Because even though the speed is constant but the object is continuously changing the direction and hence it accelerates because of the change in direction of the velocity vector.

2. True, Newtons = kg-m/s2

3. False.

it is not true always, for example if the block is resting on an inclined plane the normal force = mg cos(theta)

or when there is a force acting in the direction or opposite to the direction of normal force that also needs to be considered when applying Newton's second law.