Mechanics

Question 1

Centre of mass

Answer 1

The single point through which all the mass of an object can be act.

Question 2

Conservation of energy

Answer 2

Energy cannot be created or destroyed- it can only be transferred into different forms.

Question 3

Conservation of Momentum

Answer 3

The total momentum of a system before an event, must be equal to the total momentum after the event, assuming no external forces act.

Question 4

Couple

Answer 4

Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation.

Question 5

Effciency

Answer 5

The ratio useful output to a total input for a given system

Question 6

Elastic collision

Answer 6

A collision in which the total kinetic energy of the system before the collision is equal to the total kinetic energy of the system after the collision.

Question 7

Equilibrium

Answer 7

For an object to be in equilibrium, both the resultant force and the resultant moment acting on the object must be equal to zero

Question 8

Impulse

Answer 8

The change of momentum of an object when a force acts on it. It’s equal to the product of the force acting on the object and the length of time over which it acts.

Question 9

Inelastic collision

Answer 9

A collision in which the total kinetic energy of the system before the collision is not equal to the kinetic energy of the system after the collsion.

Question 10

Moment

Answer 10

The product of force and the perpendicular distance from the line of action of the force to the pivot

Question 11

Momentum

Answer 11

Product of an object’s mass and velocity

Question 12

Newton’s first law

Answer 12

An object will remain in its current state of motion, unless acted on by a resultant force. An object requires a resultant force to be able to accelerate.

Question 13

Newton’s second law

Answer 13

The sum of the forces acting on an object is equal to the rate of change of momentum of the object

Question 14

Newton’s third law

Answer 14

Every action has an equal and opposite reaction. If an object exerts a force in another object, then the other object must exert a force back, that is opposite in direction and equal in magnitude.

Question 15

Principle of moments

Answer 15

For an object to be in equilibrium, the sum of the clockwise moment acting about a point must be equal to the sum of the anticlockwise moments acting about the point

Question 16

Scalar

Answer 16

A scalar quantity only has a magnitude. E.g. speed, mass and temperature

Question 17

Vector

Answer 17

A vector quantity has both a magnitude and direction.

E.g. velocity, displacement and acceleration.

Question 18

Terminal speed

Answer 18

The maximum speed of an object that occurs when the resistive and driving forces acting on the object are equal to each other.