Question

A force of 75 N at an angle of 15° to the direction of motion moves a chair 3 m. Which change would result in more work being done on the chair?

using 60 N of force
moving the chair 2 m
increasing the angle to 20°
decreasing the angle to 10°

Answer 1

Work = F d cosθ. Original: W = 75·3·cos15° ≈ 225·0.9659 ≈ 217.3 J.

Compute each change (same other parameters unless stated):

- Use 60 N: W = 60·3·cos15° ≈ 180·0.9659 ≈ 173.9 J (less).
- Move 2 m: W = 75·2·cos15° ≈ 150·0.9659 ≈ 144.9 J (less).
- Increase angle to 20°: W = 75·3·cos20° ≈ 225·0.9397 ≈ 211.7 J (less).
- Decrease angle to 10°: W = 75·3·cos10° ≈ 225·0.9848 ≈ 221.6 J (more).

So decreasing the angle to 10° gives more work done.