The Third Law of Motion 1 Newtons Third

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=mxv

• 5. Rewrite Newton’s 2 nd Law –

• 5. Rewrite Newton’s 2 nd Law – – Recall, a=(vf-vi)/time

• 5. Rewrite Newton’s 2 nd Law – – Recall, a=(vf-vi)/time – Recall, f = m x a

• 5. Rewrite Newton’s 2 nd Law – – Recall, a=(vf-vi)/time – Recall, f = m x a – Combine these relationships -

• 5. Rewrite Newton’s 2 nd Law – – Recall, a=(vf-vi)/time – Recall, f = m x a – Combine these relationship • Net force = (change in momentum)/time

• 5. Rewrite Newton’s 2 nd 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 2 nd 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