6. Centre of mass and linear momentum

Question 1

steps in drawing a free body diagram

Answer 1

1. identify the object of interest
2. draw force vectors acting on the object of interest
3. choose a convenient co-ordinate system
4. apply newton’s laws in each co-ordinate direction

Question 2

Centre of mass formula

Answer 2

x = 1/M x ∑mi x ri

x = position of centre of mass
M = total mass of the system that consists of n objects of mass mi at respective positions

x= m1x1 + m2x2
______________
m1 +m2

Question 3

Momentum formula

Answer 3

P = mv

Pi = m1v1i + m2v2i = m1vf + m2vf

Question 4

When is there a change in momentum?

Answer 4

When there is a net force