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Physics > Dynamics > Flashcards

Dynamics Flashcards

1
Q

Define speed

A

Speed is the distance travelled by an object in a certain time

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2
Q

Define average speed

A

The total distance travelled divided by the total time taken

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3
Q

How do you calculate average speed?

A

To calculate the average speed of a journey we need to measure a distance and a time

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4
Q

Name 3 distance measuring equipments

A

Ruler,Trimble wheel, meter stick, measuring tape

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5
Q

Name 3 time measuring equipments

A

Stop watch, clock, stopclock

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6
Q

The relationship used to measure average speed is?

A

v = d/t (this will be written as d = vt on the relationship sheet)

where:
v = speed measured in metres per second (ms^-1)
d = distance measured in metres (m)
t = time measured in seconds (s)

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7
Q

What is instantaneous speed

A

Instantaneous speed is the speed of a moving object at any particular instant in time.

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8
Q

How do you measure instantaneous speed?

A

You need to measure the distance travelled in a very short time, this can be done by using a ruler to measure the length of an object and a light gate connected to a timer to measure the time it takes for the object to pass a fixed point

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9
Q

Define acceleration

A

Acceleration is the change in speed of a moving object per second

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10
Q

How to calculate acceleration?

A

Change speed/ time, as a formula this is written as a = v-u/ t

where:
a = acceleration measured in metres per second per second (ms^-2)
v = final speed measured in metres per second (ms^-1)
u = initial speed measured in metres per second (ms^-1)
t = time measured in seconds (s)

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11
Q

Explain deceleration

A

If an object is decelerating the final speed will be less than the initial speed, this means the change in speed will be negative and so will the anwser for a in the formula

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12
Q

In a speed time graph how can you find the acceleration

A

The acceleration in a speed time graph is the gradient of the line

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13
Q

How do you work out the distance travelled using a speed time graph

A

Calculate the are under the graph

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14
Q

What is friction

A

Friction is a force that acts in the opposite direction to an objects movement.

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15
Q

What does friction do?

A

It slows down or stops a moving object.

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16
Q

When does a frictional force occur

A

A frictional force always acts when two surfaces are rubbing against each other.

17
Q

How can you decrease how much friction effects an object?

A

Lubricating surfaces (eg oiling)
Decreasing surface area
Smoothing surfaces
Streamlining the shape

18
Q

What does the term “balanced forces” mean

A

Balanced Forces means the forces acting on an object are equal in size but act in opposite directions.

19
Q

State Newton’s first law

A

An object at rest will remain at rest and an object in motion will remain in motion with a constant speed in a straight line unless acted on by an unbalanced force.

20
Q

Why do things slow down if we don’t keep pushing them?

A

Because of friction

21
Q

If you push something in space what happens and why

A

It keeps on moving at a constant speed for ever because there is no friction

22
Q

State Newtons 2nd law

A

When an unbalanced force acts on an object it will accelerate. F = ma

where:
F = unbalanced force measured in newtons (N)
m = mass measured in kilograms (kg)
a = acceleration measured in metres per second per second (ms^-2)

23
Q

What is the definition of mass in physics

A

Mass is a measure of how much matter there is in a substance

Measured in kilograms (kg)

24
Q

What is the definition of weight in physics

A

Weight is the force due to gravioty acting on a mass.

Weight is measured in Newtons (N) and it is a force.

25
Q

What causes the weight of an object

A

The pull of gravity

26
Q

What is gravitational field strength

A

The force gravity applie to a mass of 1 kg

27
Q

What is the gravitational field strength on earth.

A

9.8 N kg^-1

28
Q

What is the formula for weight

A

W = mg

where:

W = weight measured in newtons (N)
m = mass measured in kilograms (kg)
g = gravitational field strength measured in newtons per kilogram (N kg^-1)

29
Q

State Newtons 3rd law

A

If object A exerts an action force on object B, object B will exert an equal and opposite reaction force on A.

30
Q

What is freefall?

A

Freefall is any motion where gravity is the only force acting upon it.​

Newton’s Laws apply to freefall.

Because this is an unbalanced force the object will keep accelerating (at 9.8 ms^-2 on earth)

31
Q

What is terminal velocity?

A

Terminal velocity is the constant vertical speed reached by a falling object when the forces acting on it are balanced.

Physics (7 decks)

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