1. The momentum of a body is calculated by multiplying it’s mass with it’s velocity.

2. The symbol for momentum is p.

3. The formula is p = mv

4. Simple example.
The 2kg trolley is moving at 3ms^-1 to the right. Calculate it's momentum.

The momentum would be:
p = mv
p = (2)(3)
p = 6kg.m.s^-1 right

5. Momentum is a vector quantity hence the need for stating direction in the final answer.

6. If the momentum for a 4kg trolley is 20kg.m.s^-1 leftwards, calculate the velocity.
p = mv
20 = 5v
v = 4m.s^-1 left