Question

a person holds a string that is attached to a box. the person allows the box to move straight downward at a constant speed v, as shown. the weight of the box is 5 n. which of the following claims about the tension in the string is correct?
a the tension must be zero.
b the tension must be less than 5 n but greater than zero.
c the tension must be equal to 5 n.
d the tension must be greater than 5 n.

Explanation:

Step1: Analyze the motion of the box

The box is moving at a constant speed, so its acceleration \(a = 0\). According to Newton's second law \(F_{net}=ma\), since \(a = 0\), \(F_{net}=0\).

Step2: Identify the forces acting on the box

The two forces acting on the box are the gravitational force \(F_g = 5N\) (weight of the box) acting downward and the tension force \(T\) in the string acting upward.

Step3: Apply Newton's second law

Since \(F_{net}=0\), we have \(T - F_g=0\) (taking upward as positive). Substituting \(F_g = 5N\) into the equation, we get \(T=F_g\).

Answer:

C. The tension must be equal to \(5N\)