# Calculating tension in a rope

1. Jun 7, 2014

### PHYSIC NEWBEE

1. The problem statement, all variables and given/known data

A 82 kg sled is pulled forward from rest by a snowmobile and accelerates at 2.0 m/s2 [forward] for 6.0 s. The force of friction acting on the sled is 120 N [backwards]. The total mass of the snowmobile and driver is 460 kg. The drag force acting on the snowmobile is 540 N [backwards]

(a) Determine the tension in the rope.
(b) Calculate the force exerted by the snowmobile that pushes the sled forward.

2. Relevant equations
T= M X G

3. The attempt at a solution
T=MG
T=(82)(9.8)-(460)(2)
T=803.6 N-920 N
=116.4N
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jun 7, 2014

### Nathanael

If the sled is $82kg$ and accelerates forward at $2\frac{m}{s^2}$ then what must be the net force on the sled?

What forces contribute to that net force?

3. Jun 7, 2014

### tms

That is not generally true. What is true is that $F = ma$, that is, the net force equals the mass times the acceleration. The acceleration of the sled in this problem is not due to gravity., but due to the tension in the rope. Gravity does play a part, but only in determining the frictional forces.