Dynamics Wagon Problem

Tags:
1. Mar 28, 2016

IbrahimA

1. The problem statement, all variables and given/known data
A child is pulling a wagon of mass 7.38 kg up a hill inclined at an angle of 14.3 degrees to the horizontal. The child applies a force parallel to the hill. The acceleration of the wagon is 6.45 cm/s^2 up the hill. Friction is negligible. Determine the magnitude of (a) the force applied by the child, and (b) the normal force on the wagon.

FBD Diagram I drew:

Correct Answers on book:
(a) 18.3 N
(b) 70.1 N

2. Relevant equations
Fnet = ma

(a) Fnet = -Fgx + Fa
(b) Fn = -Fgy

3. The attempt at a solution
(a)
Fnet = (-Fgx) + Fa
ma = m(-g)(cos14.3) + Fa
(7.38)(0.0645) = (7.38)(-9.8)(cos14.3) + Fa
71.9 N = Fa

(b)
Fn = Fgy
Fn = (7.38)(-9.8)(cos14.3)
Fn = 11.7 N

2. Mar 28, 2016

TSny

Welcome to PF!

Note that you've used the cosine function for getting both Fgx and Fgy.

Make sure your calculator is in "degree mode".

3. Mar 28, 2016

IbrahimA

I literally just checked it now, its was on radians. I redid the calculations and they are correct.
Thank you so much.

4. Mar 28, 2016

TSny

Good work!

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted