Mechanics

Question 1

What is a vector?

Answer 1

A quantity which had both magnitude and direction

Question 2

What is a scalar?

Answer 2

A scalar quantity had a magnitude only

Question 3

State what is means by the following modelling assumption: Particle
And state what the term means

Answer 3

Dimensions of the object are negligible

1) Mass of the object is concentrated at a single point
2) Rotational forces and air resistance can be ignored

Question 4

State what is means by the following modelling assumption: Rod
And state what the term means

Answer 4

All dimensions but one are negligible

1) Mass is concentrated along a line
2) No thickness
3) Rigid

Question 5

State what is means by the following modelling assumption: Lamina
And state what the term means

Answer 5

Object with area but negligible thickness

1) Mass is distributed across a flat surface

Question 6

State what is means by the following modelling assumption: Uniform body
And state what the term means

Answer 6

Mass is distributed evenly

1) Mass of the object is concentrated at a single point at the geometrical centre of the body (centre of mass)

Question 7

State what is means by the following modelling assumption: Light object
And state what the term means

Answer 7

Mass of the object is small compared to other masses

1) Treat object as having 0 mass
2) Tension the same at both ends of a light string

Question 8

State what is means by the following modelling assumption: Inextensible string
And state what the term means

Answer 8

A string that does not stretch under load

1) Acceleration is the dame in objects connected by a taut inextensible string

Question 9

State what is means by the following modelling assumption: Smooth surface

Answer 9

1) Assume that there is no friction between the surface and any object on it

Question 10

State what is means by the following modelling assumption: Rough surface
And state what the term means

Answer 10

If a surface is not smooth

1) Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force

Question 11

State what is means by the following modelling assumption: Wire
And state what the term means

Answer 11

Rigid thin length of metal

1) Treated as one dimensional

Question 12

State what is means by the following modelling assumption: Smooth and light pulley

Answer 12

1) Pulley has no mass

2) Tension is the same on either side of the pulley

Question 13

State what is means by the following modelling assumption: Bead
And state what the term means

Answer 13

Particle with a hole in it for threading on a wire or string

1) Moves freely along wire/string
2) Tension is the same on either side of the bead

Question 14

State what is means by the following modelling assumption: Peg
And state what the term means

Answer 14

A support from which a body can be suspended or rested

1) Dimensionless and fixed
2) Can be rough or smooth as specified

Question 15

State what is means by the following modelling assumption: Air resistance
And state what the term means

Answer 15

Resistance experienced as an object moves through air

1) Usually modelled as being negligible

Question 16

State what is means by the following modelling assumption: Gravity
And state what the term means

Answer 16

Force of attraction between all objects

1) Assume that all objects with mass are attracted towards the Earth
2) Earth’s gravity is uniform and acts vertically downwards
3) g is constant and is taken as 9.8 m/s²

Question 17

Define velocity

Answer 17

Rate of change of displacement

Question 18

Average velocity =

Answer 18

Displacement from starting point / Time taken

Question 19

Average speed =

Answer 19

Total distance travelled / Time taken

Question 20

Define acceleration

Answer 20

The rate of change of velocity

Question 21

What is the constant acceleration equation with s, u, v and t in it?

Answer 21

s = ((u + v)/2)t

Question 22

What is Newton’s First Law of motion?

Answer 22

An object at rest will stay at rest and that an object moving with constant velocity will continue to move with constant velocity unless an unbalanced force acts on the object

Question 23

What will a resultant force on an object cause?

Answer 23

Will cause the object to accelerate in the same direction as the resultant force

Question 24

What is Newton’s second law?

Answer 24

The force needed to accelerate a particle is equal to the product of the mass of the particle and the acceleration produced. F = ma

Question 25

What is Newton’s third law?

Answer 25

For every action there is an equal and opposite reaction

Question 26

Describe the forces if a rigid body is on the point of tilting

Answer 26

The reaction at any other support (or the tension in any other wire/string) is zero

Question 27

When is a particle/rigid body in static equilibrium?

Answer 27

If it is at rest and the resultant force acting on the particle is zero

Question 28

Describe what is true for a body in static equilibrium:

Answer 28

1) The body is stationary
2) The resultant force is zero
3) The resultant moment is zero