Mechanics and Materials

Question 1

What is a moment of a force about a point?

Answer 1

the force multiplied by the perpendicular distance from the line of action of the force to the point

Question 2

Equation for moment?

Answer 2

moment = Force * perpendicular distance to line of action of force from the point

Question 3

What is a couple?

Answer 3

A pair of coplanar forces, where the two forces are equal in magnitude but act in opposite directions

Question 4

What does coplanar mean?

Answer 4

They are forces within the same plane

Question 5

Equation for moments in a couple?

Answer 5

Moment = Force * perpendicular distance between the lines of action of forces

Question 6

What does the principle of moments state?

Answer 6

For an object to be in equilibrium, the sum of anticlockwise moments is equal to sum of clockwise moments

Question 7

What is an objects centre of mass?

Answer 7

Is the point at which an objects mass acts

Question 8

What does it mean if an objects centre of mass is described as uniform?

Answer 8

The centre of mass will be exactly at the objects centre.

Question 9

What is momentum?

Answer 9

mass*velocity

Question 10

Is momentum always conserved?

Answer 10

Yes

Question 11

What is the rate of the change of momentum?

Answer 11

Force

Question 12

What is impulse?

Answer 12

Change in momentum - force * change in time

Question 13

Area under a force time graph is equal to what?

Answer 13

change in momentum or impulse

Question 14

What do seat belts, air bags and crumple zones in a car do to a passenger when there is a collision?

Answer 14

Increases the impact time on the car or the passenger so force on the car and passenger decreases.

Question 15

What is an Elastic collision?

Answer 15

Where both momentum and kinetic energy are conserved

Question 16

What is an inelastic collision?

Answer 16

where only momentum is conserved where as kinetic energy is converted into other forms of energy - kinetic energy may be larger or smaller afterward