Mechanics Flashcards

1
Q

What is a vector?

A

A quantity which had both magnitude and direction

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2
Q

What is a scalar?

A

A scalar quantity had a magnitude only

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3
Q

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

A

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

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4
Q

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

A

All dimensions but one are negligible

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

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5
Q

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

A

Object with area but negligible thickness

1) Mass is distributed across a flat surface

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6
Q

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

A

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)

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7
Q

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

A

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

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8
Q

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

A

A string that does not stretch under load

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

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9
Q

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

A

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

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10
Q

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

A

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

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11
Q

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

A

Rigid thin length of metal

1) Treated as one dimensional

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12
Q

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

A

1) Pulley has no mass

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

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13
Q

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

A

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

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14
Q

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

A

A support from which a body can be suspended or rested

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

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15
Q

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

A

Resistance experienced as an object moves through air

1) Usually modelled as being negligible

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16
Q

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

A

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

17
Q

Define velocity

A

Rate of change of displacement

18
Q

Average velocity =

A

Displacement from starting point / Time taken

19
Q

Average speed =

A

Total distance travelled / Time taken

20
Q

Define acceleration

A

The rate of change of velocity

21
Q

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

A

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

22
Q

What is Newton’s First Law of motion?

A

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

23
Q

What will a resultant force on an object cause?

A

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

24
Q

What is Newton’s second law?

A

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

25
Q

What is Newton’s third law?

A

For every action there is an equal and opposite reaction

26
Q

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

A

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

27
Q

When is a particle/rigid body in static equilibrium?

A

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

28
Q

Describe what is true for a body in static equilibrium:

A

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