Solving for Speed After Man Shoves Stone: A Misstep?

[apiwowar]

A 75 kg man lying on a surface of negligible friction shoves a 74 g stone away from himself, giving it a speed of 2.3 m/s. What speed does the man acquire as a result?

so i have m1v1f + m2v2f = 0

since I am solving for v2f i get v2f = (.074*2.3)/75 = .002

but wileyplus says that wrong, did i make a mistake anywhere?

 

[NobodySpecial]

Try thinking about the answer first.
A man standing on ice (or on a skateboard if you live below 49deg) pushes a block that weighs about the same as him.

How do you expect him to move.

 

[PhanthomJay]

A 75 kg man lying on a surface of negligible friction shoves a 74 g stone away from himself, giving it a speed of 2.3 m/s. What speed does the man acquire as a result?

so i have m1v1f + m2v2f = 0

since I am solving for v2f i get v2f = (.074*2.3)/75 = .002

but wileyplus says that wrong, did i make a mistake anywhere?

I think it's a significant figure thing. You need another digit to get 2 sig figures in your result. Don't forget the units.

 

[NobodySpecial]

opps sorry - read that as a 74kg stone.

 

[Qua]

A 75 kg man lying on a surface of negligible friction shoves a 74 g stone away from himself, giving it a speed of 2.3 m/s. What speed does the man acquire as a result?

so i have m1v1f + m2v2f = 0

since I am solving for v2f i get v2f = (.074*2.3)/75 = .002

but wileyplus says that wrong, did i make a mistake anywhere?

Add an extra zero at the end, so the answer would be .0020 and you got your self another significant digit and still maintaining the correct value. Woot!