## abdullah1995 one year ago A block weighing 300 N slides downwards on the angled surface shown at an initial velocity of 2.5 m/s. At t = 0, a force P with the given orientation is applied until the block stops. Knowing that it took 5 seconds for the block to stop and that the coefficient of kinetic friction μk = 0.1, determine the magnitude of P (picture included in the post)

1. abdullah1995

|dw:1438818371044:dw|

2. abdullah1995

First i broke the forces into components. Added the Fn and Friction force on the diagram and labelled 300N force acting downwards. Once i broke the forces into components i got two equations, one for forces acting on the y-axis and the second for forces acting on the x-axis. -0.4226P + Fn - 281.90 = 0 ---------- Equation (1) 0.9063P - F(f) +102.606 = 0 ---------- Equation (2) Note that F(f) is force of friction. Then i knew that F(f) = Fn x 0.1 from the question so i replaced it F(f) with it. -0.4226P + Fn - 281.90 = 0 0.9063P - 0.1Fn +102.606 = 0 After this i solved these two equations simultaneously and found the value of P. My question/confusion is regarding all the other information given in the question, such as the initial velocity, time etc. I feel like i have done something wrong here. Any guidance would be highly appreciated.

3. johnweldon1993

Hint* If the sum of the forces in the 'x' direction = 0...the block would never have moved. this is a dynamic problem not statics your 'x' equation should be equal to "ma"

4. johnweldon1993

You have the times and velocities in order to solve for 'a' and use it to find your 'P'

5. abdullah1995

Ah ok i got it Thanks a lot ! Can you please help me with one more problem?

6. abdullah1995

@johnweldon1993

7. johnweldon1993

If I can of course!

8. abdullah1995

9. abdullah1995

I think i have done part A, but i am completely stuck on part B :/

10. johnweldon1993

First, can you post what you got from part A

11. abdullah1995

BE: -4i + 8j -8k ---> BE = 12m |dw:1438834319191:dw|

12. abdullah1995

L(i) + 6(j) -8(k) ---> CD = $\sqrt{L^2 +100}$ L|dw:1438834536640:dw|

13. abdullah1995

this is what i have.

14. abdullah1995

@johnweldon1993

15. abdullah1995