Physics help please?

Let’s determine the weights of the sofa and box.

For the sofa, weight = 100 * 9.8 = 980 N

For the box, weight = 50 * 9.8 = 490 N

This is a torque problem. I suggest that you draw a diagram of this problem. To solve this problem, I use the end of the sofa that James is holing as the pivot point. Since the weight of the sofa is at its center, it is 2 meters from the pivot point. The weight of the box is 4 meters from the pivot point. Let’s calculate these two clockwise torques.

For the sofa, torque = 980 * 2 = 1960

For the box, torque = 490 * 4 = 1960

Total clockwise torque = 3920

4 – 0.5 = 3.5 m

This is Sarah’s distance from the pivot point.

Counter clockwise torque = F * 3.5

F * 3.5 = 3920

F = 3920 ÷ 3.5 = 1120 N

If you round this number to 2 significant digits, e is the correct answer.

The forces must be balanced. Assuming both people are exerting upward forces with no horizontal components, the sum of those forces equals the total weight:

J + S = 150kg * g

From the round numbers of the answer choices, I'll guess they're rounding g to 10 m/s^2.

And the torques must be balanced. Measuring torque around the center of the sofa:

J and the weight of the box are both at 2m, and S is at 1.5m.

J and the weight of the box produce torques in one direction and S produces torque in the opposite direction.

Assuming symmetry, the weight of the two halves of the sofa exert equal and opposite torques, so those add to zero.

J * 2m + 50kg * 10 m/s^2 * 2m = S * 1.5m

This gives a system of equations to solve.