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April 29, 2016

# Homework Help: physics

Posted by Aileen on Sunday, November 7, 2010 at 9:22pm.

I calculated parts a, b, c, but cannot figure out d. I tried combining all the forces and adding them but I am missing something?

There is an 18 kg box on a 32degree incline. a HORIZONTAL force of 150 N is given to the box

a) How much work is done by the horizontal force F = 150 N on the 18-kg block of the figure when the force pushes the block 5.1 m up along the 32degree incline? ľk = 0.13.

b) How much work is done by the gravitational force on the block during this displacement? -480 J

c) How much work is done by the normal force? 0J

d) What is the speed of the block (assume that it is zero initially) after this displacement?
I tried adding up (Fpcostheta - mgcostheta -Ffriction) but it doesn't work

thank you!!
• physics - Brian, Tuesday, November 9, 2010 at 7:49pm

Use the work-energy principle:

Wnet=1/2mv^2-1/2mv^2

Initial velocity is zero therefore:

Wnet=1/2mv^2

Ans: 4.3 m/s

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