Solving Momentum of a Ball Homework: Man's Speed & Average Force

[phizics09]

Homework Statement

An 80 kg man standing at rest on a smooth, level ice surface throws a 200g ball horizontally with a speed of 25 m/s, relative to the Earth. a) With what speed and in what direction does the man move? b) If the man throws six such balls every 5.0s, what is the average force acting on him?

Homework Equations

Ft=mv

The Attempt at a Solution

I got part a using the conservation of momentum equation, but I don't get how to do b.
Can anyone help?

 

[Delphi51]

Use F = ma = M*Δv/Δt
Every throw gives him a bit of Δv. Multiply it by 6 for 6 throws.

 

[phizics09]

Okay, I got it. Thanks!

 

[Delphi51]

Most welcome!

 

[technician]

Force = rate of change of momentum
Force = change in momentum per second
Force = change in momentum of each interaction x number of interactions per second
This is another way to say what Delphi51 said.

 

[phizics09]

Okay thanks!