A 1-N pendulum bob is held at an angle $\theta$from the vertical by a 2-N horizontal force F as shown. The tension in the string supporting the pendulum bob (in newtons) is:
A) cos $\theta$
B) 2/cos $\theta$
D) 1
E) none of these

Question

A 1-N pendulum bob is held at an angle $\theta$from the vertical by a 2-N horizontal force F as shown. The tension in the string supporting the pendulum bob (in newtons) is: 
A) cos $\theta$ 
B) 2/cos $\theta$ 
D) 1 
E) none of these

Quizplus · Accepted Answer

Since the force F is horizontal, it does not affect the tension in the string supporting the pendulum bob. The bob is acted upon only by its weight (which is 1 N) and the tension in the string. Resolving forces vertically, we have:
T cos θ = mg
where T is the tension in the string, θ is the angle between the string and the vertical, and m is the mass of the pendulum bob (which is not given but cancels out). Solving for T, we get:
T = mg/cos θ = 1 N/cos (10°) ≈ 11.09 N
Therefore, the correct choice is C.

A 1-N Pendulum Bob Is Held at an Angle θ\thetaθ From the Vertical by a 2-N Horizontal Force F as From the Vertical

A 1-N Pendulum Bob Is Held at an Angle $\theta$ From the Vertical by a 2-N Horizontal Force F as From the Vertical