# Homework Help: Pulling a sled - find friction & force exerted on puller

1. Oct 5, 2008

### BoogieBot

1. A child pulls a sled with mass 9.0kg through the snow(note: no coefficient of friction given, but there _is_ friction between sled & snow). The sled accelerates at 1.0 m/s2. The rope exerts 27Nt on the sled in the forward direction.

a) what force must the rope exert on the child (magnitude & direction)?

b) What is the magnitude of the frictional force on the sled (hint: it's in the opposite direction of the sled's motion)?

2. Relevant equations

F=ma

3. The attempt at a solution

a) 27 Nt, due to Newton's 3rd law, in the opposite direction of the child/sled's motion.

b)
Frope - Fk = Ftotal = ma

Frope = Fk + ma

27 = Fk + (9 * 1)

18Nt = Fk

are my answers correct? Should their signs be negative, because they are in the opposite direction of the sled's motion? Have I made any glaring omissions regarding the rope's tension?

2. Oct 5, 2008

### Staff: Mentor

Looks good to me. Magnitudes are always positive. (The abbreviation for Newton is N, not Nt.)