15. Forces and Matter

Question 1

How many forces are required to compress, bend or stretch an object?

Answer 1

More than one; it takes multiple forces (in different directions) to deform an object.

Question 2

Explain the relationship between the force applied and the extension of an elastic object.

Answer 2

The extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded.

Question 3

What is meant by an inelastic (plastic) deformation?

Answer 3

• A deformation which results in the object being permanently changed.
• The object doesn’t return to its original shape when the force is removed.

Question 4

What type of energy is stored in a spring when it is stretched?

Answer 4

Elastic potential energy.

Question 5

What can extension be replaced with in the equation for spring force?

Answer 5

Compression.

Question 6

What is the difference between elastic and inelastic distortion?

Answer 6

• An elastic distortion is a temporary change. The object reverts to its original shape once the forces are removed.
• An inelastic distortion leads to a permanent change in shape. It is irreversible.

Question 7

How can you calculate the work done/stored in stretching a spring?

Answer 7

Energy (J) = 0.5 x Spring Constant (N/m) x Extension² (m²)

E = ¹/₂kx²

Question 8

When is there a linear relationship between force and extension?

Answer 8

When an object is deforming elastically; when it has not yet reached the limit of proportionality.

Question 9

When is there a nonlinear relationship between force and extension?

Answer 9

When the limit of proportionality has been exceeded, and the object is undergoing plastic deformation.