# Hooke's Law Study Sheet

Hooke's Law Study Sheet

- Created by: Thomas
- Created on: 04-11-12 09:00

First 443 words of the document:

Physics Factsheet

www.curriculum-press.co.uk Number 83

Experiments- Hooke's Law and Young Modulus

Factsheet 27 went through the elasticity theory required at A-level (and

probably further) in some detail. Practical Hints:

1. Use only small masses. This gives you more data points. It also

In this Factsheet we will look at some of the experimental work linked to makes it less likely you will exceed the limit of proportionality.

the topic. We will concentrate on how best to make the practical work 2. Repeat readings with decreasing masses to ensure there is no

produce accurate and reliable data, and the graphical work and calculations hysteresis effect.

resulting. 3. Some springs are manufactured with the coils forced so tightly together

that it takes a significant force to begin separating them. This may

Hooke's Law provides information on the properties of a specific device affect the starting point of the graph. Use only the straight-line section

(spring, length of wire, etc). The Young modulus gives us a value for a to find the gradient.

material (steel, copper, glass, etc).

Example:

Hooke's Law refers to a specific device; the Young modulus A student performs an experiment to find the spring constant of a

refers to a material. steel spring, obtaining these results:

Hooke's Law (revision): Mass / g Ave. extension / 10-3 cm

0.0 0.0

F 5.0 0.1

10.0 0.5

P 15.0 0.8

20.0 1.3

25.0 1.8

30.0 2.1

0 e Find the spring constant.

In the proportional region, between O and P (the limit of proportionality):

Solution:

Rewrite the table:

F = ke where F is the applied force (N)

e is the extension (m) Weight/10-3N Ave. extension / 10-3 m

k is the spring constant (Nm-1)

0 0

49 1

Practical Hint: 98 5

Throughout these practicals, always do repeats and averages where 147 8

possible, and take care with significant figures and units. 196 13

245 18

294 21

Finding the spring constant, k, of a steel spring.

F/10-3N

300

This is a standard practical going back to

250

GCSE level. A series of masses are carefully

added to the mass holder, and measurements 200

of extension and weight are recorded in a

m table. 150

100

The results are then graphed: 50

F

0 2 4 6 8 10 12 14 16 18 20 22 24

The spring constant, k, e/10-3m

is the gradient (from k = F / e). k = gradient = (200 × 10-3 ) / ( 17 × 10-3 ) = 12 Nm-1

Notice the care that must be taken with the units, and that the best

e straight line should not be started from the origin in this situation.

1

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