Newton's Laws - Mission NL2 Detailed Help

A ball is thrown vertically upwards. After the ball is released and is moving upwards towards its peak, it slows down. During this time ...

Newton's First Law of Motion:
An object at rest will stay at rest; an object in motion will stay in motion with the same speed and direction, unless acted upon by an unbalanced force.

Many beginning students of Physics believe that an object will always move in the direction of the force which acts upon it. But don't be fooled! Forces are associated with the acceleration direction of an object, not with the direction the object is moving. As such, a forward moving object does not necessarily need a forward force. A forward force would only be needed to speed the object up; if the object is slowing down, a backward force would be required to cause its backwardacceleration. And what if the object is moving at a constant speed? Then all the forces acting upon it are balanced.

Direction of Acceleration:
If an object is slowing down, then the direction of its acceleration is opposite the direction that the object is moving. A rightward moving object that is slowing down has a leftward acceleration. And a leftward moving object that is slowing down has a rightward acceleration.