Materials Model Answers

Question 1

Define yield stress

Answer 1

The force per unit area at which the material extends considerably/strain increases considerably

Question 2

What happens to 2 trucks, A and B, which are travelling towards each other (different masses and different velocities) when they collide?

Answer 2

The trucks move in opposite directions/rebound

Momentum of B after collision is the same as that of A before the collision and vice versa

Question 3

Ball is falling towards Earth. Explain, with reference to the conservation of momentum, the effect that the motion of the golf ball has on the motion of the Earth from the instant it is released until it bounces at the plate.

Answer 3

As ball falls, momentum of ball towards Earth = momentum of Earth towards ball
On impact momentum of Earth and momentum of ball both become zero
After impact, momentum of ball away from Earth = momentum of Earth in opposite direction

Question 4

Tensile stress definition

Answer 4

Force per unit cross sectional area

Question 5

Tensile stress definition

Answer 5

Extension per unit length