Question

A pendulum bob of mass 50 g is suspended on a string from the ceiling of an elevator which is moving downwards with an acceleration 1.5 ms−2. Draw the free body diagram using the non-inertial frame of reference and determine the tension in the string. (Take g = 10 ms−2)

Answer 1

Answer on Question #65597 – Physics – Mechanics – Relativity

Question:

A pendulum bob of mass $50\mathrm{g}$ is suspended on a string from the ceiling of an elevator which is moving downwards with an acceleration 1.5 ms-2. Draw the free body diagram using the non-inertial frame of reference and determine the tension in the string. (Take $\mathrm{g} = 10$ ms-2)

Solution:

By Newton's second law:

$$\vec {F} = m \vec {a};$$

At the same time:

$$\vec {F} = \vec {T} + m \vec {g};$$

So, we have:

$$m \vec {a} = \vec {T} + m \vec {g};$$

Or, in scalar form:

$$m a = T - m g \Rightarrow T = m g + m a = m (g + a) = 0. 0 5 \cdot (1 0 + 1. 5) = 0. 5 7 5 N;$$

Answer:

$$T = 0. 5 7 5 N.$$

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