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

Assuming that the string is connected to both F and M, the tension in the string must be the same throughout the entire string due to the frictionless surfaces. Therefore, the tension in the string equals the force required to lift M, which is given by F_g = mg, where g is the acceleration due to gravity (9.8 m/s²). 
Substituting m = 1.0 kg and g = 9.8 m/s², we have F_g = (1.0 kg)(9.8 m/s²) = 9.8 N. 
Since the tension in the string is equal to F_g, the answer is C) 3.8 N.

If F = 80 N and M = 1