Question

Pulley system is attached to a massless board as shown below. The board pivots only at the pivot point. A 10 kg mass M sits exactly in the middle of the board

If the angle q is 30º, the minimum force F necessary to lift the 10 kg mass is -

• A. 12.5 N
• B. 25 N
• C. 50 N
• D. 100 N

Answer 1

Answer: (B)

25 N

Answer 2

Tension in string is F

Mg $\frac { L } { 2 }$ = 2FL

F = $\frac { \mathrm { Mg } } { 4 }$ = 25 N