Required Practical 4: Determination Of Young Modulus

Question 1

Describe a method to gain a value for young modulus

Answer 1

1) set up apparatus
2) measure the inital length l of the test wire using a meter ruler
3) add a mass holder to each wire so they are taught and measure the initial scale reading
4) add an additional 100g mass to the test wire and record the new scale reading
5) calculate extension by subtracting initial scale reading from new scale reading and record this value
6) repeat experiment adding a 100g mass each time
6) carry out whole experiment twice more to calculate mean values of extension for each value of m
7) measure the diameter of the wire using a micrometer at 5 different points on the wire
8) calculate the mean diameter of the wire
9) calculate the cross-sectional area for the wire
10) calculate the force for each mass by using F=mg
11) plot a graph of F against e and draw a line of best fit
12) young modulus = gradient x l / A

Question 2

What is the independent variable for this experiment

Answer 2

The force / load

Question 3

What is the dependant variable

Answer 3

Extension

Question 4

What are some control variables

Answer 4

• the metal used for the wire
• the thickness of the wire
• the original length of the wire

Question 5

What safety measures should be taken

Answer 5

• wear safety goggles as wire could snap
• place a sand tray underneath the masses incase the wire breaks and the masses fall

Question 6

Describe a way you can reduce the uncertainty

Answer 6

• make sure the original length of wire is as long as possible to reduce uncertainty in measurement
• use a vernier scale
• remove the masses after each value recorded to make sure the wire returns to its original length