A 90 kg man lying on a surface of negligible friction shoves a 69 g stone away from himself, giving it a speed of 8.3 m/s. What speed does the man acquire as a result?

Question

anonymous · Answer

you are familiar with the 3rd law motion right, in the case mentioned same force F will be applied on both bodies. we can find F by using the equation 
F=ma
for the stone, i.e as same applied on the man but the mass is much more greater than the mass of the stone hence the acceleration will be less than that acquired by stone.
and so by putting the value of F and mass m of man we can find the acceleration of the man.

austinl · Answer

I am really unsure of what I need to be doing. Physics is not my strong suit... sorry.

ivancsc1996 · Answer

No, I think you need to tackle this problem through conservation of momentum. Have you seen momentum?

austinl · Answer

Yes, momentum i know.
$$p = m v$$

ivancsc1996 · Answer

Well basically:$$m _{st}v _{st}=m _{man}v _{man} \rightarrow v _{man}=\frac{ m _{st}v _{st} }{ m _{man} }$$

ivancsc1996 · Answer

Were st=stone

austinl · Answer

Would the speed of the man be 0.00636 m/s then?

austinl · Answer

It is, Thanks!

ivancsc1996 · Answer

Great :)

anonymous · Answer

oh shoot! you had to find the speed. i thought it was acceleration, sorry about that. 
ivancsc 1996 is right .
but both approaches will give the same result.