# Velocity attained by sled

OK i'm stuk on a physics question involving Newton's Laws of motion.

Question:

Boy gives his sister ride on sled by exerting force of 300 N[E].
Frictional resistance amounts to 200 N. If sister and sled have combined mass of 50 kg, and if boy starts from rest and pushes for 5 sec., find:

a) the sled's acceleration
b) velocity attained by sled in 5 sec.
c) distance travelled by sled in 5 sec.

PLZ try to help and show step by step solutions

Reply ASAP thanx

## Answers and Replies

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jcsd
Science Advisor
Gold Member
It's not the policy here to do peoples homewrok, but I'll give you the relevant formulae:

F = ma, v = u + at, s = &frac12;(u + v)t

F is force, m is mass, a is acceleration ,v is final velocity, u is intial velocity, s is displacemnet and t is time.

Reply

Wait, how do we find initial velocity?

Thanx for help.

HallsofIvy
Science Advisor
Homework Helper
We don't. But since the problem asked for the "velocity attained" (i.e. the increase in velocity), we can take it to be 0- that way the final velocity WILL be the increase in velocity.