A mass m = 13 kg rests on a frictionless table and accelerated by a spring with spring constant k = 4104 N/m. The floor is frictionless except for a rough patch. For this rough path, the coefficient of friction is μ_k = 0.5. The mass leaves the spring at a speed v = 3.3 m/s.

1) How much work is done by the spring as it accelerates the mass?

2) How far was the spring stretched from its unstreched length?

3) The mass is measured to leave the rough spot with a final speed v_f = 1.4 m/s.

How much work is done by friction as the mass crosses the rough spot?

4) What is the length of the rough spot?

5) In a new scenario, the block only makes it (exactly) half-way through the rough spot. How far was the spring compressed from its unstretched length?

6) In this new scenario, what would the coefficient of friction of the rough patch need to be changed to in order for the block to just barely make it through the rough patch?

So I found everything except for number 3 and 5 and I really need help because I tried to plug in the numbers to the equation and it didn't work? I had 58.25 for number 3 but it wasn't right? And I used the 58.25 for question 4 and it was right, but not sure why it wouldn't be for number 3. Not sure if it's negative? And I tried to look up number 5, but it wasn't helpful since I couldn't really find anything on it. Thanks!

Edited September 29, 20196 yr by JustAStudent
I missed a question

Show your work

43 minutes ago, JustAStudent said:

So I found everything except for number 3 and 5 and I really need help because I tried to plug in the numbers to the equation and it didn't work? I had 58.25 for number 3 but it wasn't right? And I used the 58.25 for question 4 and it was right, but not sure why it wouldn't be for number 3. 

No the work is not negative but I just got 58. 045 Joules, using g = 10

So as swansont said

How did you get your value?

Then we can compare notes.