The Third Law of Motion
1. Newton’s Third Law of Motion –
1. Newton’s Third Law of Motion – To every action force there is an equal and opposite reaction force
1. Newton’s Third Law of Motion – To every action force there is an equal and opposite reaction force When one object exerts a force on a second object, the second one exerts a force on the first that is equal in size and opposite in direction
1. Newton’s Third Law of Motion – To every action force there is an equal and opposite reaction force When one object exerts a force on a second object, the second one exerts a force on the first that is equal in size and opposite in direction Forces are equal, but they are NOT balanced
1. Newton’s Third Law of Motion – To every action force there is an equal and opposite reaction force When one object exerts a force on a second object, the second one exerts a force on the first that is equal in size and opposite in direction Forces are equal, but they are NOT balanced Examples: trampoline, swimmer, rocket propulsion
Newton’s Laws 1. First Law – (inertia) – an object moving at a constant velocity keeps moving at that velocity unless a net force acts on it; an object at rest stays at rest unless a net force acts on it
Newton’s Laws 2. Second Law – (f = m x a) – a net force acting on an object causes the object to accelerate in the direction of the net force
Newton’s Laws 3. Third Law – (action-reaction pairs) To every action force there is an equal and opposite reaction force
2. Gravity and the planets –
2. Gravity and the planets – The orbit of every planet is affected by the gravitational pulls from all the other planets
3. Momentum–
3. Momentum– A property that a moving object has because of its mass and velocity (speed&direction)
3. Momentum– A property that a moving object has because of its mass and velocity (speed&direction) Momentum is related to how much force is needed to change the motion of a moving object
3. Momentum– A property that a moving object has because of its mass and velocity (speed & direction) Momentum is related to how much force is needed to change the motion of a moving object Increasing either the speed or the mass of an object makes it harder to stop
4. Calculating Momentum –
4. Calculating Momentum – momentum = p
4. Calculating Momentum – momentum = p momentum = mass x velocity
4. Calculating Momentum – momentum = p momentum = mass x velocity p = m x v
5. Rewrite Newton’s 2nd Law –
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time Recall, f = m x a
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time Recall, f = m x a Combine these relationships -
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time Recall, f = m x a Combine these relationship - Net force = (change in momentum)/time
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time Recall, f = m x a Combine these relationships - Net force = (change in momentum)/time F = (mvf - mvi) / time
5. Rewrite Newton’s 2nd Law – Recall, a=(vf-vi)/time Recall, f = m x a Combine these relationships - Net force = (change in momentum)/time F = (mvf - mvi) / time (mvf=final momentum, mvi=initial momentum)
6. Law of Conservation of Momentum –
6. Law of Conservation of Momentum – Momentum of an object doesn’t change unless it mass, velocity, or both change
6. Law of Conservation of Momentum – Momentum of an object doesn’t change unless it mass, velocity, or both change HOWEVER, momentum can be transferred from one object to another
6. Law of Conservation of Momentum – Momentum of an object doesn’t change unless it mass, velocity, or both change HOWEVER, momentum can be transferred from one object to another The Law states that if a group of objects exerts forces only on each other, their total momentum doesn’t change