# Pendulum Lab

## Introduction

What makes a pendulum work?

If you were building a clock how would you figure out what size and mass of pendulum you need?

First we need to do some experiements to see what affects the speed (time) of a pendulum. The most obvious ones to look at are:

- Mass
- Length

Does a heavier weight on the end make the pendulum faster or slower?

What about making the pendulum longer, what happens?

## 1) Period vs Length

- Wrap 1m of string around the end of the stick
- Hold the stick on the table with about 20-30cm sitcking out past the edge
- Tie 4 metal weights on the end of a piece of string
- Adjust the length of string to 60cm

(Measure from the**middle of the weights**to the stick) - Raise the mass to about 45 degrees
- Time how long 10 full periods (swings) take
- Repeat for each length shown in the table

Length (m) | 10 Periods (s) | 1 T (Period) (s) |
---|---|---|

0.60 | ||

0.50 | ||

0.40 | ||

0.30 | ||

0.20 |

### Question

What effect does the pendulum's length have on its period?

## 2) Period vs Mass

- Tie 8 metal weights on the end of the string
- Measure and record the mass on the end of the string
- Adjust the length of string to 60cm

(Measure from the**middle of the weights**to the stick) - Raise the mass to about 45 degrees
- Measure and record how long 10 full periods (swings) take
- Repeat for masses of 4, 2, and 1 wieghts

# Weights | Length (m) | Mass (g) | 10 Periods (s) | 1 T (Period) (s) |
---|---|---|---|---|

8 | 0.60 | |||

4 | 0.60 | |||

2 | 0.60 | |||

1 | 0.60 |

### Question

What effect does the pendulum's mass have on its period?

## 3) DIY Clock

### Challenge

Can you build a pendulum with a period of exactly 1 second?

How long does it need to be?

Can you make it keep time for 1 minute?

*(If you are VERY good at algebra, you could solve the equation below, for L, to figure it out too)*

## 4) Calculated vs Measured

Now we need to look at how our measurments compare to theory using maths.

T = Period (in seconds)

L = length (in meters)

g = gravity (9.81m/s^{2})

### Example calculation for a scientific calculator:

60cm = 0.6m

### Example calculation for a simple calculator:

(We must follow the order of operations manually)

60cm = 0.6m

### Calculate the theorical period for all the lengths you measured:

Length (m) | T Period (s)Measured Experimental |
T Period (s)Calculated Theorectical |
% Error |
---|---|---|---|

0.60 | |||

0.50 | |||

0.40 | |||

0.30 | |||

0.20 |