Momentum and Newton's laws of motion (3.1)

What is mass? and what is its relation to motion?

Mass - the amount of matter in an object

Thus mass is a property of an object that resists change in motion

What is weight? and how does it differ to mass?

Weight - the effect of a gravitational field on mass

W=mg

Where W is in N

m is in Kg

g is in ms^-2

Weight vs Mass

Weight can differ depending on the gravitational pull whereas mass is constant. E.g. on the moon someone will have a lower weight but the same mass

What is Newton’s first law?

1^st law - a body will remain at rest or move with constant velocity if no resultant force acts on it

What is Newton’s second law?

2^nd law - the rate of change in momentum is proportional to the magnitude of the force

F_NET = ma

Where F_NET is in N

Where m is in Kg

Where a is in ms^-2

What is Newton’s third law?

3^rd law - if one body exerts a force on another, it will experience a force by the other body, which is equal in magnitude and opposite in direction

Forces always occur in pairs

The force pairs must be:

• The same type of force

• The same magnitude

• Opposite in direction

• Acting on different objects

What is linear momentum?

Linear momentum - the product of mass and velocity

p=mv

Where p is momentum in kgms^-1

Where m is mass in kg

Where v is velocity in ms^-1

Momentum is a vector

How can force be defined in terms of momentum?

Force - the rate of change of momentum

F=Δp/Δt

Where F is force in N

Where Δp is change in momentum in kgms^-1

Where Δt is change in time in s

Δp = p_final - p_initial

F is the resultant force

Δp is also known as impulse