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PAT Oxford > Mechanics > Flashcards

Mechanics Flashcards

1
Q

When is an object in equilibrium?

A

No resultant force and no turning force (sum of moments is zero)

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2
Q

Define moment (including equation)

A

Moment = force x perpendicular distance from line of action of the force to the axis or point of rotation

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3
Q

Moment of a couple?

A

Moment of a couple =FD

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4
Q

When does a falling object reach terminal velocity?

A

When it’s weight (gravitational pull) is equal to the drag force and it no longer accelerates, it falls at a constant velocity

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5
Q

Newton’s First Law?

A

An object remains at rest/constant velocity unless acted on by a resultant force

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6
Q

Newton’s Second Law?
Include equations

A

Resultant force is proportional to the rate of change of momentum.
F = change in momentum/t
F=ma if m is constant and a is uniform

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7
Q

Newton’s Third Law?

A

Force exerted by A on B is in opposite direction, same type and equal to the force exerted by B on A

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8
Q

In an elastic collision, what is conserved?

A

Momentum is conserved
Kinetic energy is conserved

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9
Q

In an inelastic collision, what is conserved?

A

Momentum is conserved
Kinetic energy is NOT conserved

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10
Q

What does the area under a force time graph represent?

A

The impulse (change in momentum)

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11
Q

What does the are under a force displacement graph represent?

A

Fs, work done or energy transferred

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12
Q

In W=Fs, what conditions need to be true for it to hold?

A

Force must be constant and the displacement must be the distance in the direction of the force.

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13
Q

What does Hooke’s Law state?
Equation?

A

That the extension of a spring is proportional to the force applied provided the limit of proportionality is not exceeded
F=kx

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14
Q

What effect does a parallel spring system have on the spring constant?

A

kt = k1 + k2 + …
The spring constant increases

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15
Q

What effect does a series spring system have on the spring constant?

A

1/kt = 1/k1 + 1/k2 + …
The spring constant decreases

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16
Q

What effect does a parallel spring system have on the extension?

A

Extension decreases

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17
Q

What effect does a series spring system have on the extension?

A

Extension increases

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18
Q

What does the gradient of a force extension graph represent for something that obeys Hooke’s Law?

A

The spring constant

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19
Q

Define friction

A

Force that acts between two surfaces that meet

20
Q

Define air resistance

A

A drag force experienced when moving through air

21
Q

For circular motion, where is the object accelerating?

A

Towards the centre

22
Q

In circular motion, ____ is always a tangent to the objects path

A

In circular motion, velocity is always a tangent to the objects path

23
Q

What are the centripetal acceleration equations?

A

a = v^2 /r
a = w^2 r

24
Q

What is the difference between angular velocity and angular frequency?
What is the equation?

A

Angular velocity is a vector and used for circles.
Angular frequency is a scalar and used for SHM and waves.
w=2 pi f

25
Q

In circular motion, how do you work out the force acting towards the centre of the circle?

A

F= mv^2 /r
F=mw^2r

26
Q

In a loop de loop, what will the reaction force be at the top?

A

R=(mv^2/r)-mg

27
Q

In a loop de loop, what will the reaction force be at the bottom?

A

R=(mv^2/r)+mg

28
Q

What is amplitude for SHM?

A

Magnitude of the max displacement (+ve)

29
Q

What is displacement for SHM?

A

Distance from rest position (+ve or -ve)

30
Q

What is frequency for SHM?

A

Number of oscillations per unit time

31
Q

What is the period for SHM?

A

Time for one complete oscillation

32
Q

SHM has:
an __ proportional to __ from equilibrium position
an a in ____ direction to displacement

A

SHM has:
an ACCELERATION proportional to DISPLACEMENT from equilibrium position
an acceleration in OPPOSITE direction to displacement

33
Q

What is the acceleration equation for an object in SHM?

A

a=- w^2 x

34
Q

What is the displacement equation for an object in SHM?

A

x=Acos(wx)

35
Q

When is vmax in SHM?

A

At the equilibrium position
vmax =+- wA

36
Q

When is amax in SHM?

A

At max displacement
amax = -w^2 A

37
Q

For a simple pendulum, what is the time period?
What does it tell us?

A

T=2pi sqrt(L/g)
Where L is the length of the string.

T is independent of x or A

38
Q

For a mass-spring system, what is the time period?
What does it tell us?

A

T=2pi sqrt(m/k)
Where k is the spring constant.

Bigger k, higher f and smaller T
Heavier mass, T increases

39
Q

SHM graphs:
x against t is a ___ graph (starting from equilibrium position)

A

a sin graph

40
Q

SHM graphs:
v against t is a ___ graph (starting from equilibrium position)

A

a cos graph

41
Q

SHM graphs:
a against t is a ___ graph (starting from equilibrium position)

A

a negative sin graph

42
Q

When in equilibrium position, a pendulum has:
- max __
- min __

A

In equilibrium:
- max kinetic energy
- min potential energy (0)

43
Q

When at max displacement, a pendulum has:
- max __
- min __

A

At max displacement:
- max potential energy
- min kinetic energy (0)

44
Q

In a vertical mass spring system:
When compressed,
- Ek is __
- Gpe is __
- Epe is __

A

In a vertical mass spring system:
When compressed,
- Ek is 0
- Gpe is max
- Epe is min

45
Q

In a vertical mass spring system:
When at equilibrium,
- Ek is __
- Gpe is __
- Epe is __

A

In a vertical mass spring system:
When at equilibrium,
- Ek is max
- Gpe is 1/2 max
- Epe is 1/2 max

46
Q

In a vertical mass spring system:
When most stretched,
- Ek is __
- Gpe is __
- Epe is __

A

In a vertical mass spring system:
When most stretched,
- Ek is 0
- Gpe is min
- Epe is max

PAT Oxford (5 decks)

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