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S111 Topic 3 - why does it snow > Part 2 - Why Does Snow Fall > Flashcards

Part 2 - Why Does Snow Fall Flashcards

1
Q

Define the term gravity?

A

The natural force that makes things fall to the ground.

It is the force that attracts one object of mass to another object of mass.

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2
Q

Who developed the universal law of gravity?

A

Sir Isaac newton

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3
Q

Are rules/laws theories or facts?

A

They are theories

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4
Q

What does ‘in motion’ refer to?

A

Moving in some way

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5
Q

What is Newton’s first law of motion?

A

That an object remains at rest or moves in a straight line at a constant speed unless it is acted on by an unbalanced force.
Also known as inertia

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6
Q

What is an unbalanced force?

A

A force that changes the motion of an object either at rest or moving in a straight line at constant speed.

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7
Q

What is friction?

A

The force resisting motion or the force that is created when two surfaces move, or try to move, across each other.

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8
Q

What is the idea of an unbalanced force?

A

It is the idea that an unbalanced force comes about from the possibility that an object can be acted on by more than one force at a time

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9
Q

How many forces are acting on a glass resting on a table?

A

Two

The downward force of gravity due to the gravitational attraction of the earth on the glass

And

The upward push of the table surface on the glass

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10
Q

How does the upward force of a table with a glass resting on it create a force?

A

The upward push arises from the slight compression of the surface of the table when the glass is placed on it.
The downwards pull of gravity on the glass forces it against the table surface, and as a result the atoms in the surface layers of the table are pushed slightly closer together.
This is a little like compressing a spring and, just like a spring the atoms push back. The net result is an upward push force on the glass.

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11
Q

Are the forces balanced or unbalanced of a glass resting on a table?

A

The forces on the glass balance. The downward force from gravity is equal to the upward force from the table, so the glass remains at rest.

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12
Q

Now imagine the somewhat unrealistic situation where the surface of the table is perfectly frictionless. The glass is given a quick nudge to set it moving.
Describe the movement of the glass and the forces acting upon it?

A

The glass will move in a straight line at a constant speed. The only forces on the table are the downward force of Tacitus and the upward push f the table. These are still balanced and so the glass moves in a straight line at a constant speed

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13
Q

Now suppose there is a table that is more realistic and there is friction acting between the glass and the table.
What would you need to do to make the glass move at a constant speed and why?

A

This time, the glass would need to be pushed continuously to keep it moving at a constant speed in a straight line.

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14
Q

How many forces does a glass in a table being pushed in a straight line at a constant speed along a table with friction have acting on it?

A

The downward force of gravity
The upward push of the table
The push force
The force of friction

So 4

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15
Q

If the push force is removed from a glass on a table being pushed in a straight line at a constant speed along with a table with friction what would happen?

A

The push force has to initially exceed the force of friction. If the push force was removed, the force of friction with bring the glass to rest

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16
Q

What are the balance of forces on a snowflake just after it has left a cloud and is falling to the ground (ignoring air resistance)?

A

When the snowflake has just left a cloud and is falling to the ground, the forces are unbalanced. There is a downward force of gravity on the snowflake.

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17
Q

What is the balance of forces on a snowflake just after it has hit the ground and come to rest. Assume the ground is below 0 degrees and the snowflake does the not melt?

A

The snowflake is at rest on the ground and so the forces are balanced. There is the upward force of the ground pushing up on the snowflake and there is a downward force of gravity pulling down the snowflake

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18
Q

What is speed?

A

It is the measure of the ‘rate of movement’

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19
Q

What is velocity?

A

It means both the speed and direction of motion.

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20
Q

A car is moving at a constant speed but not in a straight line, how does this fit with Newton’s first law of motion?

A

According to Newton’s first law of motion because the velocity of the car is changing it must mean that there is an unbalanced force acting on the car.

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21
Q

Is it correct to say the velocity of a car is 22 m s-1

A

No it is not as the velocity also means direction

The correct way of saying it is velocity of a car is 22 m s-1 in the northwest direction

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22
Q

Is it correct to say the speed of a car is 22 m s-1 in the northwest direction?

A

No it is not the velocity would only mean you had to state the direction
The correct answer would be
The speed of the car is 22 m s-1

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23
Q

An object moves with constant velocity unless it is acted on by an ……………?

A

Unbalanced force

24
Q

Can an object at rest also be at a constant velocity?

A

When an object is at rest it has zero velocity and high of course is a constant velocity

25
Q

An unbalanced force will cause a change in …….?

A

A change in velocity

That is a change in speed or a change in direction or a change in both.

26
Q

What does Newton’s second law in motion help us to calculate?

A

It helps us to calculate the changes in speed and direction of an object which arise from an unbalanced force acting on it.

27
Q

What is the change in speed called?

A

Acceleration

28
Q

What is meant by the term gradient?

A

The amount the road goes up or down in a given distance

E.g. 1 metre height to every 10 metres in distance

29
Q

How do you calculate gradience?

A

Change in vertical value divided by the change in horizontal value

Or
Gradient = rise divided by run

30
Q

How do you calculate the speed of an object?

A

Speed = distance travelled divided by time taken

Or
Change in position divided by time taken

31
Q

How do you calculate the magnitude of acceleration?

A

Change in speed divided by the time taken

32
Q

When using the term magnitude of acceleration what does the use of the word magnitude mean?

A

It implies that acceleration also has direction

33
Q

What can losing speed also be known as?

A

Decelerating

Negative acceleration

34
Q

What is the SI unit of acceleration?

A

m s-2 (to the power of minus 2)

35
Q

Do you think that an object being spun at a constant speed is accelerating?

A

Yes it is

36
Q

Whenever there is a change in speed, a change in direction or a change in both there is an …………?

A

Acceleration

Acceleration is a change in velocity

Just like velocity acceleration has both magnitude and a direction

Acceleration is a change in speed

37
Q

An object does not accelerate unless it is acted on by an ……………?

A

Unbalanced force

38
Q

If an object is acted on by an unbalanced force it will ………..?

A

Accelerate

39
Q

Consider a train slowing down on a straight track.

A) is the train showing a change in velocity?
B) is there an acceleration?
C) is an unbalanced force acting?

Justify your answer for

A

A) for a train to slow down on a straight track, there is no ch age in direction, but there is a change in speed, so there is a change in velocity.

B) as there is a change in velocity there is by definition an acceleration

C) from Newton’s first law of motion, an unbalanced force must be acting

40
Q

Consider a car going around a bend at a constant speed.
A) is the car showing a change in velocity?
B) is there an acceleration?
C) is an unbalanced force acting?
Justify your answer

A

A) yes, there is a change in velocity, in this case, a change in direction.

B) as there is a change in velocity there is by definition an acceleration

C) from Newton’s first law of motion, an unbalanced force must be acting

41
Q

What is Newton’s second law of motion?

A

The magnitude of the unbalanced force on an object equals the mass of that object multiplied by the magnitude of its acceleration

F = ma

42
Q

How do you calculate force?

A

Mass x acceleration

43
Q

What is the symbolic notation for the calculation of force?

A

F = ma

44
Q

What symbol is used for force?

A

F

45
Q

What symbol is used for mass?

A

m

46
Q

What symbol is used for acceleration ?

A

a

47
Q

If the mass of an object is greater, how will be acceleration be affected?

A

For an unbalanced force of any given magnitude, the greater the mass then the smaller the acceleration.

48
Q

What is inertia?

A

It is property of matter by which it continues in its existing state of rest or uniform motion in a straight line unless the state is changed by an external force

Reluctance to accelerate

Inertia is a noun which means a tendency to do nothing and remain unchanged

49
Q

What is the unit of mass?

A

Kg

50
Q

What is the SI unit of force?

A

Kg m s-2 (power of minus 2)

Which is called a newton (N)

51
Q

In words how do you describe kg m s-2?

A

Kilogram metres per second per second

52
Q

If force = mass/acceleration… how would you calculate acceleration?

A

Force/mass =acceleration

53
Q

What is Newton’s third law?

A

For every action there is an equal and opposite reaction

54
Q

What is a gravitational force?

A

It’s the force that attracts a body (meaning any physical object) towards the centre of the earth.

55
Q

What does Newton’s law of gravity state?

A

It states that the gravitational force between two objects increases when either their masses increase or when they are brought closer together

56
Q

Imagine that much of the material that makes up the interior of the earth disappeared. How would the gravitational force of the earth on you change?

A

Newton’s law of gravity concerns the mass of, and the distance between two objects. The distance of the earths centre would not change. However, removing much of the material that makes up the interior of the earth would reduce its mass. This means the gravitational force on you would decrease because the mass of the earth had decreased

57
Q

How does gravity affect acceleration of an object that is falling?

A

The acceleration due to gravity experienced by any object that is falling freely close to the earths surface is constant : it has the same value, irrespective of the mass of the object

S111 Topic 3 - why does it snow (3 decks)

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