# Velocity attained by sled

#### Phyzor

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 #### jcsd

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.

#### Phyzor

Wait, how do we find initial velocity?

Thanx for help.

#### HallsofIvy

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.

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