A level physics moments question please explain how the answer to (a) is 7.5N and the answer to (b) is 5.7N

Explanation:

a) Sum of moments about the pivot:

∑τ = Iα

(10 kg × 10 m/s²) (0.3 m) + F (-0.4 m) = 0

F = 75 N

b) Sum of moments about the pivot:

∑τ = Iα

(20 N) (0.3 m) + (20 N) (-0.2 m) + F (-0.7 m) = 0

6 Nm − 4 Nm + F (-0.7 m) = 0

F = 2.9 N

e

explanation:

there is no change in the electric potential energy as it is in rest on both conditions.

see earlier