Everything Science Grade 11

CHAPTER 12. FORCE,MOMENTUM AND IMPULSE 12.5

Example 26: Momentum of a Soccer Ball

QUESTION

A soccer ball of mass420 g is kicked at 20m·s−^1 towards the goal post. Calculate the

momentum of the ball.

SOLUTION

Step 1 : Identify what information is given and what isasked for

The question explicitly gives

• the mass of the ball, and


• the velocity of the ball
  The mass of the ball must be converted to SI units.

420 g = 0,42kg

We are asked to calculate the momentum of theball. From the definitionof

momentum,

p = m· v

we see that we need themass and velocity of theball, which we are given.

Step 2 : Do the calculation

We calculate the magnitude of the momentumof the ball,

p = m· v

= (0,42kg)(20m· s−^1 )

= 8,4kg· m· s−^1

Step 3 : Quote the final answer

We quote the answer with the direction of motion included, p = 8,4 kg·m·s−^1

in the direction of the goal post.

Example 27: Momentum of a cricket ball

QUESTION

A cricket ball of mass 160 g is bowled at 40 m·s−^1 towards a batsman. Calculate the momen-