Finding net force and acceleration from force components

[NINHARDCOREFAN]

I'm stuck on two problems 1 is #8(please see the pdf file):
I know I have to solve this equation with this:
F=MA
I calcualated F by taking the magnitude of Fx and Fy:
Fx=390*cos(9)i+335*cos(-28)
Fy=390*sin(9)i+335*sin(-28)

I got F as 687.756
and the mass is given: 3819kg

So I divided those and I got the answer as .180 but the comp. says it's wrong.

The second problem is 12(please see the pdf file):
I know I have to do this:
F = m*g-m*a*cos(angle)
(is it right?)

(I calculated the acceleration and it is right)
so F = 3.35*9.8-3.35*5.67*cos(27)
and I got 26.06. What's wrong? with this?

Thanks in advance for the help.

 

[enigma]

The first looks fine to me. Check your sig figs.

The second, I'm not exactly sure what it's asking for. It looks to me like it's asking what the normal force is (equal & opposite from what the block applies to the incline). I'm not sure though.

 

[M98Ranger]

Hi there,

I can see that you have put a lot of effort into solving these problems. It's great that you are using the correct equations and calculating the values correctly. However, there might be some minor mistakes in your calculations that are leading to the wrong answers.

For the first problem, make sure you are using the correct signs for the angles in your calculations. Also, check if you are using the correct units for the force and mass. Sometimes small errors like these can make a big difference in the final answer.

For the second problem, it seems like you are using the correct equation and values. Double check your calculations and make sure you are using the correct values for the angle and acceleration. Also, pay attention to the units of your answer.

If you are still stuck, I would suggest asking a classmate or your teacher for help. Sometimes having a fresh pair of eyes can help identify mistakes that we might have missed.

Keep up the good work and don't get discouraged. Keep practicing and you will get the hang of these problems. Good luck!

 

[M98Ranger]

Hi there,

Thank you for reaching out for help. I understand that you are stuck on two problems and need help by tonight. I will do my best to assist you.

For the first problem (#8), it seems like you have the correct approach by using the equation F=MA and calculating Fx and Fy. However, when calculating Fy, there seems to be a mistake in the calculation. The correct values for Fx and Fy should be:

Fx = 390*cos(9) + 335*cos(-28) = 379.35 N
Fy = 390*sin(9) + 335*sin(-28) = 201.49 N

Then, when you divide F by the given mass of 3819 kg, you should get an answer of 0.099 N/kg. Please double check your calculations and see if this helps you arrive at the correct answer.

For the second problem (#12), your approach is correct in using the equation F = m*g - m*a*cos(angle). However, there seems to be a mistake in your calculation for F. The correct calculation should be:

F = 3.35*9.8 - 3.35*5.67*cos(27) = 26.26 N

Please double check your calculations and see if this helps you arrive at the correct answer.

I hope this helps. If you are still having trouble, please feel free to reach out for further assistance. Good luck with your assignment.