Friction on an Inclined Plane

  • #1
1. Homework Statement
The diagram shows a 5kg block of lead released from rest at the top of an incline. The block has a speed of 6 m/s when it reaches the bottom. The angle between the slope and the ground is 40° and the slope is 10 m long.
a) What is its PE at the top?
b) What is its KE at the bottom?
c) What is the work done by friction?
d) What must be the coefficient of friction?

2. Homework Equations
I am having trouble finding the friction. Once i find the friction, i know how to find the coefficient force of friciton using Ffr=mu*Fn.

3. The Attempt at a Solution
For part a first I found what the height was by doing 10(sin(40))=Height and got 6.43 m. Than i plugged that into PE=mgh... 5(9.8)(6.43) ... getting 315.07J ...
For part b I used KE=1/2(m)(v2) ... 1/2(5)(62) ... getting 90J ...

Answers and Replies

  • #2
What is the component of the weight normal to the surface? That will be fn.
What is the component of the weight along the surface?
In the absence of the friction, what will be the KE at the bottom?
Difference in the KE = fr*d, where d is the distance moved by the block.
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