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Physics > Motion and Forces > Flashcards

Motion and Forces Flashcards

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1
Q

What are vectors?

A

Quantities with a magnitude and direction.

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2
Q

What are scalars?

A

Quantities with just a magnitude.

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3
Q

What are some examples of vector quantities?

A

Force, acceleration, displacement and velocity.

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4
Q

What are some examples of scalar quantities?

A

Length, speed, volume and distance.

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5
Q

What is speed?

A

A scalar that is a measure of the distance an object travels in a given time.

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6
Q

What is velocity?

A

A vector that is a measure of speed in a certain direction.

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7
Q

What would a runner’s velocity be if he did exactly one lap of a track?

A

It would be zero because he started where he ended up.

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8
Q

What is the speed formula for scalars?

A

d=vt / distance (metres) = speed (metres per second) multiplied by time (seconds).

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9
Q

What is the speed formula for vectors?

A

s=vt / displacement (metres) = velocity (metres per second) multiplied by time (seconds).

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10
Q

What are the three figure bearings for the four major compass points?

A

North = 000, East = 090, South = 180, West = 270

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11
Q

How would you calculate displacement when an object travels in two perpendicular directions?

A

You would plot the two distances of each direction into a triangular format, and calculate the hypotenuse using Pythagoras’ theorem.

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12
Q

How would you calculate the bearing for the direction that an object travels if given two perpendicular distances that it has already moved?

A

You would use trigonometry to calculate the relevant angle. Once you know which corner of the triangle is needed, you determine the names of the two adjacent sides and use that information to select the necessary section of the SOH CAH TOA mnemonic to calculate the bearing.

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13
Q

If a trolley is released from rest, and passes through the light gate at the end of the ramp, what would happen to the speed reading if the light gate was moved further up the slope of the ramp and the process was repeated?

A

The trolley will have less time to accelerate, so the speed value will decrease.

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14
Q

If a trolley is released from rest, and passes through the light gate at the end of the ramp, what would happen to the acceleration reading if the light gate was moved further up the slope of the ramp and the process was repeated?

A

The acceleration measurement would be completely unchanged because the slope of the ramp is at an equal gradient, meaning the acceleration will be constant (exactly the same at any point).

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15
Q

What is acceleration?

A

The vector that is a measure of the change in velocity per second.

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16
Q

What does it mean if a car is moving at 10 ms-2?

A

It is increasing its velocity by ten every second (or accelerating).

17
Q

What is the formula for acceleration?

A

a = v - u/t (Acceleration ms-2 = final velocity ms-1 minus initial velocity ms-1 divided by time secs.) Basically, acceleration = change in velocity over time.

18
Q

What does it mean on a velocity time graph if there is a diagonal line with a negative gradient?

A

The object in a state of uniform/constant decceleration because it is decreasing the velocity by the same amount every second.

19
Q

What does it mean on a velocity time graph if there is a diagonal line with a positive gradient?

A

The object is in a state of uniform/constant acceleration because it is increasing the velocity by the same amount every second.

20
Q

What does it mean on a velocity time graph if there is a straight line?

A

The object is at a constant speed (neither accelerating nor decelerating) because there is no change in velocity per second.

21
Q

How do you calculate the acceleration of an object on a velocity time graph?

A

You find the gradient of the line (vertical magnitude divided by horizontal magnitude).

22
Q

How do you calculate the distance an object has travelled on a velocity time graph?

A

You split the space below the line on the graph into basic shape parts, work out the area for each section using the graph numbers as width and height, and add all the values together.

23
Q

What does the y intersect mean on a velocity time graph?

A

It is the velocity the object started with. For example, if y intersect = 0 it starts at rest, but if y intersect = 10 it is travelling at 10 metres per second to start off with.

24
Q

What does the x intersect mean on a velocity time graph?

A

It is the time when the object reaches 0 velocity.

25
Q

What does it mean if the line goes below the x-axis?

A

The object is travelling backwards (decelerating with a negative velocity).

26
Q

What is a balanced pair of forces?

A

When a force has an opposite force of an equal magnitude acting in the other direction, so they effectively cancel each other out.

27
Q

What is an unbalanced pair of forces?

A

When a force acting on an object has a greater magnitude than any other opposite force.

28
Q

What can an unbalanced force cause a change in?

A

Speed, direction, shape or rotation.

29
Q

What are some examples of contact forces?

A

Air resistance (drag), friction, elastic potential, pressure and lift.

30
Q

What are some examples of non-contact forces?

A

Gravitational potential, magnetism/electromagnetism.

31
Q

What is Newton’s First Law of Motion?

A

Inertia: An object remains at rest, and an object in motion remains in motion at a constant speed unless acted on by an unbalanced force.

32
Q

What is Newton’s Second Law of Motion?

A

F = ma - force (newtons/N) = mass (kilograms/kg) multiplied by acceleration (metres per second per second/ms-2)

33
Q

What is Newton’s Third Law of Motion?

A

Action and Reaction: When two objects interact, the force on one (action) is matched by an equal and opposite force (reaction) on the other.

34
Q

What is a resultant force?

A

The overall, greatest unbalanced force acting on an object after the opposite, lesser forces have been subtracted.

35
Q

How would you calculate the resultant force if two different forces of unbalanced magnitude were acting in perpendicular directions?

A

You would calculate the hypotenuse using pythagoras’ theorum, and the direction of the force using trigonometry.

36
Q

What is mass?

A

The quantity of matter of an object. It is measured in kilograms (kg).

37
Q

What is weight?

A

The size of the gravitational pull force acting on an object. It is measured in newtons (N).

38
Q

What is the formula for weight?

A

w = mg - weight (N) = mass (kg) multiplied by gravitational field strength (Nkg-1)

Physics (3 decks)

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