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Physics > P5-forces > Flashcards

P5-forces Flashcards

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1
Q

what is the definition of acceleration

A

the change in velocity in a time period

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2
Q

equation for acceleration?

A

acceleration (m/s^2) =change in velocity(m/s) / time (s)

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3
Q

difference between speed and velocity?

A

speed is how fast you’re going. Velocity is speed in a given direction

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4
Q

what is the typical speed of a person walking?and a person running?

A

1.5m/s and 3m/s

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5
Q

average speed of a person cycling?

A

6m/s

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6
Q

average speed of: a car, a train and a plane

A

25m/s, 55m/s and 250m/s

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7
Q

what does the gradient of a distance time graph show?

A

the speed

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8
Q

what does a flat section of a distance time graph show?

A

the object has stopped moving

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9
Q

what does an upward curve and a downward curve show on a distance time graph?

A

acceleration and deceleration

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10
Q

what does a straight uphill line show on a distance time graph?

A

steady speed

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11
Q

what does the gradient of a velocity time graph show?

A

acceleration

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12
Q

a flat section of a VT graph shows…

A

steady speed

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13
Q

a straight uphill section of a VT graph shows…

a straight downward line shows…

A

acceleration and deceleration

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14
Q

a curve upwards or downwards on a VT graph shows…

A

increasing acceleration or deceleration

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15
Q

what does the area under a VT graph show?

A

the distance travelled

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16
Q

what increases as the speed of a vehicle increases?

A

the frictional forces

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17
Q

describe terminal velocity for a falling object

A

at first, the force of gravity is much larger than the frictional force, so they accelerate. then as the speed up, friction increases and this reduces acceleration until the forces are equal. The object has reached its max. speed/ terminal velocity so will fall at a steady speed.

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18
Q

what is the accelerating force for all falling objects?

A

gravity

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19
Q

what is terminal velocity determined by?

A

the object’s drag compared to it’s weight

20
Q

what does the force of friction depend on?

A

shape and area

21
Q

why does opening a parachute decrease the terminal velocity?

A

the area of the sky diver will have increased. so air resistance increases, meaning they reach their terminal velocity sooner and at a lower speed.

22
Q

explain Newton’s first law

A

If the resultant force on a stationary object is zero, the object will stay stationary. If the resultant force on a moving object is zero, it will carry on moving at the same velocity

23
Q

Newton’s second law states that a resultant force applied to an object will cause…

A

an acceleration in the same direction as the resultant force.

24
Q

resultant force=…?

A

resultant force (N)= mass(kg) x acceleration (m/s^2)

25
Q

acceleration is directly proportional to what and is indurectly proportional to what?

A

resultant force and mass

26
Q

what happens when you apply force to an object?

A

It can stretch, compress or bend

27
Q

Why do you need more than one force to make an object stretch/compress/bend?

A

If there was only one force, the object would simply move in the direction of the applied force.

28
Q

When a force stretches/compresses an object, _____ is done

A

work

29
Q

what affect does work being done on an object have on the object’s energy stores?

A

energy is transferred to the elastic potential energy store.

30
Q

what is elastic deformation?

A

the object can go back to it’s original shape after the forces have been removed. All the energy from work being done goes to the elastic potential store of the object. Happens in ELASTIC objects.

31
Q

what is inelastic deformation?

A

the object doesn’t return to it’s original shape or length when the force has been removed.

32
Q

what is the equation linking force applied, spring constant and extension?

A

Force applied (N) = Spring constant (N/m) x Extension (m)

33
Q

what is the extension of a stretched spring directly proportional to?

A

the force applied.

34
Q

what does a higher spring constant mean for an object?

A

It’s a stiffer material.

35
Q

what happens when you reach the limit of proportionality of an object?

A

the extension is no longer proportional to the force and begins increasing disproportionately.

36
Q

what is the equation for momentum?

A

momentum (kg m/s) = mass (kg)x velocity (m/s)

37
Q

is momentum a scaler or vector quantity?

A

a vector quantity. it has size AND direction.

38
Q

What is the conservation of momentum?

A

in a closed system, the total momentum before an event is equal to the total momentum after.

39
Q

what causes a change in momentum?

A

a resultant force.

40
Q

what is the equation for a force causing a change in momentum?

A

force(N)= change in momentum(kg m/s) / change in time (s)

41
Q

what is the rate of change of momentum equal to?

A

the force causing the change.

42
Q

Why are things liked cars designed to slow people down over a long period of time when they crash?

A

because if someone’s momentum changes very quickly, the forces on their body will be very large, this is more likely to cause injury.

43
Q

give two examples of cars being designed to have a slow rate of change of momentum:

A

Crumple zones-crumple on impact, increasing time taken for car to stop
seat belts-stretch slightly, increasing time taken for passenger to stop.

44
Q

What happens when a force moves an object through a distance?

A

energy is transferred, so work is done.

45
Q

what is the equation for work done?

A

work done (J)= force (N) x distance (m)

46
Q

how many Newton-metres are in 1 joule if work?

A

1Nm

Physics (4 decks)

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