# AQA AS Physics Unit 2 Revision

- Created by: S Satish
- Created on: 18-04-13 17:04

First 529 words of the document:

Materials

What is density?

This is the mass per unit volume measured in kgm3

How do you measure the density of a regular solid?

This mass is measured using a top balance

The dimensions are measured using vernier callipers or a micrometer

The volume is calculated using 4/3 x pi x r^3 for a sphere or ¼ x pi x d^2 x h

How do you measure the density of an irregular solid?

The mass is measured using a top balance

The object is immersed on a thread in liquid in a measuring cylinder

The increase in liquid level is observed and this is the object's volume

What is tension in a string?

This is the pull in the string and it is equal and opposite to the force needed to stretch a spring.

What is Hooke's Law?

The force needed to stretch a spring is directly proportional to the extension of the spring from its natural length.

F = k x delta L (k is the stiffness constant and if k is greater the spring is stiffer)

What are the equations for springs in parallel?

The position of the weight is adjusted along the rod to make the extensions of both strings the same.

Since the weight is supported by both springs W= F1 + F2 = k1 x delta L + k2 x delta L

W= k x delta L

Dividing through by delta L means that k = k1 + k2

The spring constant is both spring constants added together

What are the equations for springs in series?

The tension in both springs is the same and equal to W but their extensions are different

Delta L1 = W / k1 and delta L2 = w/k2

L = L1 + L2 so W/ k = W/k1 + W/k2 and 1/k = 1/k1 + 1/k2

What energy is stored in a stretched spring?

Elastic potential energy is stored in a stretched spring and if the spring is suddenly released, this energy is suddenly

converted to kinetic energy of the spring. Energy = area under graph = ½ x F x delta L = ½ x k x delta L^2

What is the elasticity of a solid material?

The elasticity of a solid material is its ability to regain its shape after it has been deformed or distorted and the forces that

have deformed it have been released.

What is the difference between tensile and compressive deformation?

Deformation that stretches an object is tensile whereas deformation that compresses as object is compressive.

How can we test how easily materials stretch?

The material in each case is held at its upper end and loaded by hanging weights at its lower end

A set square or pointer attached to the bottom of the weights may be used to measure the extension of the

material

The weights of the loads are increased in steps then decreased to zero

The extension of the strip of material for each load is its increases in length from its unloaded length

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