Newton's Three Laws of Motion
Number One
An object in motion will not stop unless an external force acts upon it. This is the principle of momentum
Vice versa, a stationary object will not move unless an external force acts upon it. This is the principle of inertia
Vice versa, a stationary object will not move unless an external force acts upon it. This is the principle of inertia
Number Two
An external force applied to an object can change it's direction or acceleration
This is best described via the equation F = ma
The rate of momentum is proportional to the net force applied
This is best described via the equation F = ma
The rate of momentum is proportional to the net force applied
Number Three
For every action there is an equal and opposite reaction
For example:
Take a Simple Punch
This shows how reaction forces affect the impact but don't make the punch obsolete due to different object masses
For example:
Take a Simple Punch
This shows how reaction forces affect the impact but don't make the punch obsolete due to different object masses
Here the arm is being pushed forward with a force of 80N However there is an equal and opposite reaction pushing the body back with a force of 80N Now because the body has greater mass, it doesn't move back at the same rate as the arm due to Newton's second law. However, it does move backwards and this means that the punch has less impact on the object it is impacting. |
Here the same force is being punched with, with the same reaction force This time though the body has pushed back 60N giving a reaction force of 60N Because the body has a larger mass this means the reaction force pushes the arm forwards at a faster rate using Newton's second law This means overall the forward punch has a greater force |
Momentum and Inertia
Momentum and Inertia are effectively the same thing
They are both the unwillingness of an object to change what it is doing.
Momentum is applied to objects already moving
Inertia is applied to objects stationary
Momentum is given the symbol 'p'
Momentum is defined by
momentum (kg m/s) p = mv mass (kg) x velocity (m/s)
They are both the unwillingness of an object to change what it is doing.
Momentum is applied to objects already moving
Inertia is applied to objects stationary
Momentum is given the symbol 'p'
Momentum is defined by
momentum (kg m/s) p = mv mass (kg) x velocity (m/s)
Conservation of Momentum
The momentum of a closed system remains constant unless an external force is applied
Impulse
Impulse is the change in momentum of an object
This can be worked out by using the equation
Δp = mΔv = mv - mu
This can be worked out by using the equation
Δp = mΔv = mv - mu
To work out the rate of change you divide by time
Which also shows us the connection between Force and Momentum
The rate of change in momentum equals the force of the object
Which also shows us the connection between Force and Momentum
The rate of change in momentum equals the force of the object
Δp = Rate of change in momentum
t
Thus
Δp = m(v-u)
t t
Which looks like
m(v - u) = F
t
Therefore
Δp = F
t
t
Thus
Δp = m(v-u)
t t
Which looks like
m(v - u) = F
t
Therefore
Δp = F
t