- #1

- 17

- 0

I know the answer is 28N, but I haven't yet figured it out.

I did F=ma F=(7.5)(1.41)cos13= 10.30

what didn't I do?

thanks

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- Thread starter Pencil
- Start date

- #1

- 17

- 0

I know the answer is 28N, but I haven't yet figured it out.

I did F=ma F=(7.5)(1.41)cos13= 10.30

what didn't I do?

thanks

- #2

- 163

- 0

The way I do this problem is to create a coordinate system in which the x-axis is parallel to the slope of the plane, that way we can discount forces that are acting in the y-direction (we know that the sum of the forces in the y-direction must equal 0). Only 2 forces have x components, force of the person, and gravity.

Fnet = ma

F - (mgsin13) = ma

F = (7.5 kg)(9.8 m/s^2) + (9.8 m/s^2)(7.5kg)(sin13)

F = 27.109N

this force we calculated is the force needed to create that acceleration if the person was pushing parallel to the x-axis, but we know he wants to push this horizontally so he will require a little more force.

Fcos13 = 27.109

F = 27.8N

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