P2.3

Question 1

Elastic bodies and plastic bodies

Answer 1

Elastic - objects that return to their original shape when the deforming force is removed.
Plastic - objects that do not return to their original shape when the deforming force is removed.

Question 2

Hooke’s law

Answer 2

If you double the force on a spring, its extension doubles. The extension of a spring is directly proportional to the force applied, as long as the limit of proportionality is not exceeded. This is Hooke’s law
Below the elastic limit, if you remove the force, the spring returns to its original length. Above the elastic limit it does not return to its original length.
Force applied = spring constant x extension
F = kx
Elastic potential energy = 0.5 x spring constant x extension^2

Question 3

Mass, gravity, weight

Answer 3

Weight is what we call the force of the Earth on an object when it is on the Earth’s surface.
W = m x g
Weight = mass x gravitational field strength

Question 4

Gravitational potential energy, GPE

Answer 4

GPE is the energy stored by a body, whenever it is raised through a height in a planets gravitational field.
GPE = mass x gravitational field strength x height
GPE = mgh