2 problems: potential erg & tension/friction

[Falinox]

Homework Statement

http://i754.photobucket.com/albums/xx183/reddiesel08/Question1.jpg

http://i754.photobucket.com/albums/xx183/reddiesel08/Question2.jpg

2. The attempt at a solution

http://i754.photobucket.com/albums/xx183/reddiesel08/Attempt2.jpg

http://i754.photobucket.com/albums/xx183/reddiesel08/Attempt.jpg

Need someone to check my work and help solve these two problems, thanks in advance to anyone willing to help.

 

[rock.freak667]

5 is correct, but I did not check the numbers for this one.

7, your method is correct, but your final answer is off. My calculator gives me v_i = 4.76 m/s

 

[Falinox]

5 is correct, but I did not check the numbers for this one.

7, your method is correct, but your final answer is off. My calculator gives me v_i = 4.76 m/s

Thank you! My mistake on question 7 was I forgot to multiply the 9.8(0.68) by 2 when I moved the 1/2 from the left side to the right side of the equation. I also came up with the answer 4.76 m/s.

On #5 I got the answer a = .57 m/s squared can someone verify this for me.

 

[rock.freak667]

a = 0.56645 m/s^2, so you are correct.

 

[rwisz]

I would first like to commend you for seeking help and checking your work. It shows a strong understanding of the scientific process and a desire for accuracy. In regards to the first problem, it appears that you have correctly identified the potential energy of the system as the sum of the potential energy of the mass and the potential energy of the spring. However, I would suggest using the formula for potential energy (PE = mgh) instead of calculating the work done by the spring, as the latter may not account for the change in height.

For the second problem, you have correctly identified the tension and friction forces acting on the block. However, I would recommend using the formula for kinetic friction (Ff = μkN) instead of the static friction formula, as the block is already in motion. Additionally, it may be helpful to draw a free body diagram and use Newton's second law (F=ma) to solve for the acceleration of the block.

Overall, your approach is sound and I would suggest double-checking your calculations and using the correct formulas for potential energy and friction to ensure accuracy in your solutions. Keep up the good work!