Question

The tension in a string from which a 7 kg
object is suspended in an elevator is equal to
74 N.

A) What is magnitude of the acceleration a of
the elevator? The acceleration of gravity is
9.8 m/s^2. Answer in units of m/s^2
B) What is its direction?

Answer 1

Answer:

0.77 m/s^2

Explanation:

Notice that the weight of the 7 kg mass is calculated via:

weight = m * g = 7 * 9.8 N = 68.6 N

Since the tension in the string is larger (74 N), then the elevator is moving upward and the net force on the object is equal to:

74 N - 68.6 N =  5.4 N

Which tells us that the acceleration of the object is:

F = m * a

5.4 N = 7 kg * a

a = 5.4 /7  m/s^2

a = 0.77 m/s^2

and this must be the same as the acceleration of the elevator since object and elevator are moving together.