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A man pulls a block of mass m = 20 kg up an incline at a slow constant velocity for a distance of d = 3.5 m. The incline makes an angle q = 33° with the horizontal. The coefficient of kinetic friction between the block and the inclined plane is µk = 0.2.

a) What is the work Wm done by the man?

b) What is the speed v of the block when it first reaches the horizontal surface?

c) What is the spring constant k of the spring?

d) How far up the incline d1 does the block rebound?

Relevant equations:

Wtotal = Change in Kinetic energy

Ffriction = Coefficient of friction(Fnormal)

Fspring = kx

(1/2)mv^2

I know there are the force of friction, the man, and gravity on the box. I started by saying:

Wman - Wgrav - Wfriction = Change in KE

Wgrav = m*g(in x-direction)*(Change in height) -->(20kg)(9.81m/s^2*sin33)(3.5sin33m)

Wfriction = (coefficient of friction)*m*g*distance -->(.2)(20kg)(9.81m/s^2)(3.5m)

Change in KE = 0

Wman = 823.919J, but this is not right...what am i doing wrong?

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# Homework Help: Block, Ramp, Friction, and Spring work done

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