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PHYSICS > Mechanics > Flashcards

Mechanics Flashcards

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1
Q

What must always be true when using the SUVAT equations of motion?

A

The acceleration must be uniform- if the acceleration is changing, the equations are not valid

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2
Q

What does the gradient of a Distance-time graph represent?

A

Speed

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3
Q

What does the gradient of a displacement- time graph represent?

A

Velocity

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4
Q

What does the gradient of a velocity-time graph represent?

A

Acceleration

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5
Q

Describe the shape of a velocity-time graph for an object travelling with uniform acceleration

A

If acceleration is constant, the gradient of the velocity-time graph will be constant and so it will from a straight line graph

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6
Q

Describe the shape of a velocity-time graph for an object travelling with non-uniform acceleration.

A

If acceleration is not constant, the gradient of the velocity-time graph will change and so it will form a curve

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7
Q

Compare the velocity-time graphs for a uniformly accelerating and a uniformly decelerating object.

A
  1. For an accelerating object, the gradient will be positive
  2. For a decelerating object, the gradient will be negative
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8
Q

What is a scalar quantity?

A

A scalar quantity is one that has a magnitude but not a fixed direction

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9
Q

What is a vector quantity?

A

A vector quantity is one that has a magnitude and a fixed direction

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10
Q

Give five examples of scalar quantities.

A
  1. Distance
  2. Speed
  3. Mass
  4. Energy
  5. Temperature
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11
Q

Give five examples of vector quantities.

A
  1. Displacement
  2. Velocity
  3. Acceleration
  4. Momentum
  5. Force
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12
Q

How is a vector quantity represented on a diagram?

A
  1. As an arrow
  2. The direction of the arrow represents the direction of the quantity
  3. The length of the arrow represents the magnitude of the quantity
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13
Q

What does resolving a vector involve?

A

Splitting the vector into two perpendicular components

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14
Q

Define the horizontal component of a vector at an angle to the horizontal in terms of V and theta.

A

horizontal component: X = V cos theta

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15
Q

Define the vertical component of a vector at an angle to the horizontal in terms of V and theta.

A

Vertical component: y = V sin Theta

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16
Q

Describe the relationship between the perpendicular components of a vector.

A

The perpendicular components are independent of each other.

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17
Q

How should the components of a projectile be handled when carrying out calculations? (2)

A
  1. The horizontal and vertical components are independent of each other and so should be treated separately
  2. SUVAT should be used separately for each component
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18
Q

If a projectile is moving freely under gravity, what can be said about the vertical acceleration?

A

The vertical acceleration will be the acceleration due to gravity and so will have a magnitude of 9.81 ms {-1}

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19
Q

State Newton’s first law of motion in words.

A

An object at rest will remain at rest, and an object moving with a given velocity will continue moving with that same velocity, unless acted on by an external resultant force

20
Q

State Newton’s second law of motion in words.

A

The acceleration of an object is directly proportional to the resultant force acting on it and inversely proportional to its mass

21
Q

State the defining equation of Newton’s second law of motion.

A

Resultant Force (N) = Mass(kg) x Acceleration (ms{-2}

22
Q

Can an object travelling with constant speed change direction, without an external force acting?

A

-For an object to change direction, its velocity must change.
- This means there must be an acceleration
- An acceleration cannot occur without an external resultant force acting

23
Q

Describe the forces acting on an object travelling at terminal velocity.

A
  1. The forces are balanced in both the vertical and horizontal components of its motion
  2. There is no resultant force and therefore no acceleration
24
Q

What is meant by terminal velocity?

A

-For a given set of conditions, the terminal velocity is the maximum speed of the object.
- An object has zero acceleration at terminal velocity

25
Q

State the equation used to calculate the weight of an object.

A

Weight = Mass x Gravitational Field Strength

26
Q

What is the unit of weight?

A

Newton, N

27
Q

State Newton’s third law of motion in words.

A

-Every action has an equal and opposite reaction
-This means that there is always a pair of forces acting on interacting objects, equal in magnitude, but in opposite directions

28
Q

State the equation of momentum.

A

p = mv

29
Q

What is the unit of momentum?

A

Kgms{-1}

30
Q

What is the consequence of the linear conservation of momentum?

A

The total momentum of a system before an event is always equal to the total momentum of the system after the event.

31
Q

State the equation used to calculate the work done by a force.

A

Work Done = Force x Change in distance

32
Q

what force is used when calculating the work done by a force over a distance?

A

The component of the force that is in the direction of the object’s motion.

33
Q

What is the unit of work?

A

Joules, J

34
Q

What is the work done by a force F at an angle to the horizontal when direction of motion is on the x-axis?

A

work done= F cos theta x distance travelled

35
Q

what form of energy do all moving objects have?

A

All moving objects have kinetic energy.

36
Q

what form of energy does a raised object have?

A

Gravitational Potential Energy

37
Q

State the equation used to calculate gravitational potential energy.

A

GPE = Mass x Gravitational Field Strength x height

38
Q

What is the conservation of energy?

A

The law of conservation of energy states that energy cannot be created of destroyed- it can only be transferred between different forms.

39
Q

What is power?

A

The rate at which energy or work is done.

40
Q

State two equations used to calculate power.

A

P = E/ t
P = W/ t

41
Q

What is the unit of power?

A

Watt, W

42
Q

What is the waste energy of an electrical appliance?

A

The waste energy is the energy that is not used for appliance’s intended purpose.

43
Q

State the equation relating energy and efficiency.

A

Efficiency = [Useful Energy Output] / [ Total Energy Input]

44
Q

What is the unit of efficiency?

A

Efficiency is a ratio and so doesn’t have an associated unit.

45
Q

In an elevator what is the resultant force equals to?

A

Weight of the elevator - the tension on the cable holding the elevator

46
Q

A ball is hanging on a string. Explain why the tension in the string increases immediately after the ball is kicked.

A
  • The ball accelerates towards centre of the circular path created by the string
  • This results in a force acting upwards on the string
  • this adds to the tension and thus the increase
47
Q

For a vertical string, what is the tension of the string?

A

T = mg + ma

PHYSICS (9 decks)

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