# Simple Pendulum Motion and Physical Pendulum

danield

## Homework Statement

1) Find the period of a pendulum 50 cm long when it is suspended in (a) a stationary elevator; (b) an elevator falling at the constant speed of 5.0 m/s; (c) an elevator falling at the constant acceleration of 2.0 m/s2; (d) an elevator rising at the constant speed of 5.0 m/s; (e) an elevator rising at the constant acceleration of 2.0 m/s2.

## Homework Equations

Period = 2 pi Squareroot of Length of arm/ Gravity

## The Attempt at a Solution

1) I could solve a) by simply replacing data into the formula, but I am not sure how does the change in velocity and acceleration affects the data that is where I am stuck at.

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Gold Member
A force has to be introduced to change the period.

Constant motion doesn't introduce force, only acceleration does.

danield
so that means that when the velocity is up or down 5m/s constat there is no acceleartion, so only G is taken into account?
but for the toher two, how are they calculated?

Gold Member
Gravity is an acceleration... the period is actually

P = 2*pi*sqrt(L/a)

where a is acceleration.

Gravity is always there, but in acceleration situations a will not simply be equal to G as it is in the stationary and constant motion situation.

danield
Yes i understand that part, but what i don't know is how does the up and down acceleration influence the total acceleration, this is just a hunch but i think that when acceleration is downward i would be 7.81, and when it is upward it will be 11.81, I am not totally sure about that
As for the ones where velocity is constant i think that the only acceleration acting is gravity, and I am not sure of that either..

Mentor
You are correct. The acceleration of the elevator adds (or subtracts) from the standard acceleration due to gravity (9.81 m/s^2).

danield
ok thanks very much