Newtons laws and momentum

What is newtons first law?

An object remains at rest or continuous moving with a constant velocity unless acted on by an external resultant force.

What does new proms first law mean when the resultant force is 0.

Resultant force = 0 so a = 0. The object either remains stationary or continues at a constant velocity. Zero resultant does not necessarily mean the object is stationary.

Newtons 2nd law

F =ma so the resultant force on an object = ma

How does Newton’s second law relate to momentum.

p = mv. Newton’s second law can be written as F = Change in P / Change in T. So a resultant force causes an objects momentum to change.

What happens to an objects momentum when an external resultant force acts on it?

Its momentum changes. A force can change its speed or direction

How do you apply Newton’s second law to a particle moving in a straight line?

1. Force diagram 2. Choose a positive direction 3. Resolve forces in that direction 4. Find the resultant force using F= ma

What’s Newton’s third law

When object A exerts a force on object B. B exerts a force equal in force and opposite in magnitude. Forces are equal in magnitude but opposite in direction.

How does Newton’s third law apply during a collision

During a collision a large force acts over a short time, causing a change in momentum. The force acting on each object is equal and opposite due to Newton’s third law.

How does Newton’s third law explain conservation of momentum in a collision

The 2 objects exert an equal and opposite force. Therefore they experience the same equal and opposite change in momentum so total momentum remains constant if there is no external resultant force.

A car accelerates forward, what does Newton’s second law tell you

Resultant force forwards, the driving force is greater than any opposing forces.

An object is moving but has zero resultant force. Explain how this is possible.

Newton’s first law says it will continue moving at a constant velocity.

Difference between weight and mass.

Mass is the amount of matter measured in kg. Weight is the gravitational force acting on the mass. W = mg. Mass is a property and weight depends on the gravitational field that the object is in.

Difference between F = Ma and F = p/t

F = ma used for constant mass. f = P/t used for collisions.