If F = 8.0 N and M = 1.0 kg,what is the tension in the connecting string? The pulley and all surfaces are frictionless.
A)4.1 N
B)3.5 N
C)3.8 N
D)3.1 N
E)4.8 N

Question

If F = 8.0 N and M = 1.0 kg,what is the tension in the connecting string? The pulley and all surfaces are frictionless. 
A)4.1 N 
B)3.5 N 
C)3.8 N 
D)3.1 N 
E)4.8 N

Quizplus · Accepted Answer

The tension in the string will be equal to the weight of the object being lifted (M = 1.0 kg) plus the force applied (F = 8.0 N), divided by 2 (due to the pulley). 
Tension = (M*g + F)/2 = ((1.0 kg)*(9.8 m/s^2) + 8.0 N)/2 = 3.9 N/2 = 1.95 N
However, this tension is only for one side of the string, and we need to consider both sides. So the total tension in the string is 1.95 N * 2 = 3.8 N. Therefore, the correct answer is C.

If F = 80 N and M = 1