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

When mass M is at the position shown, it is sliding down the inclined part of a slide at a speed of 2.07 m/s. The mass stops a distance S2 = 2.5 m along the level part of the slide. The distance S1 = 1.13 m and the angle q = 30.50°. Calculate the coefficient of kinetic friction for the mass on the surface.

**2. Relevant equations**

http://capa2.cc.huji.ac.il/res/msu/physicslib/msuphysicslib/13_EnergyConservation/graphics/prob27a_MechEnWFriction.gif

**3. The attempt at a solution**

I tried solving this question by:

H=1.13sin30.5

mgH+1/2mv^2-(s1+s2)u*mgcosa=0

9.8*0.5735+1/2*(2.07^2)-3.63u*9.8cos30.5=0

5.6203+2.14245=30.651u

u=0.2532

I get wrong answer all the time

can someone tell me where i went wrong?

I have another question which I have no clue hot to solve it:

The left side of the figure shows a light (`massless') spring of length 0.290 m in its relaxed position. It is compressed to 71.0 percent of its relaxed length, and a mass M= 0.250,kg is placed on top and released from rest (shown on the right).

http://capa2.cc.huji.ac.il/res/msu/physicslib/msuphysicslib/13_EnergyConservation/graphics/prob24_CompSpring.gif

The mass then travels vertically and it takes 1.50 s for the mass to reach the top of its trajectory. Calculate the spring constant, in N/m. (Use g=9.81 m/s2). Assume that the time required for the spring to reach its full extension is negligible.

Can someone tell me how to do this question?

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