P2 FORCES Flashcards

1
Q

what’s the equation for speed?

A

s=d/t

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2
Q

what’s the equation for kinetic energy?

A

KE=1/2 mv^2

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3
Q

what can you use to measure very short periods of time?

A

light gates

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4
Q

what can you use to measure a v short distance?

A

ultrasound

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5
Q

what’s the formula for acceleration?

A

a=change in v/time

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6
Q

vector vs scalar

A

vector has size and direction, scalar only has size

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7
Q

what does a horizontal line, curve and straight line mean on a distance time graph?

A

stopped, accelerating/dec, steady speed

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8
Q

whats the gradient of a distance time graph equal to?

A

speed

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9
Q

what can the gradient of a displacement time graph be?

A

positive, zero or negative

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10
Q

whats the gradient of a displacement graph equal to?

A

velocity

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11
Q

whats the gradient of a velocity time graph equal to?

A

acceleration

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12
Q

what does a straight, horizontal and curved line mean on a velocity time graph?

A

constant acceleration, steady velocity and changing acc/dec

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13
Q

what’s the area in a velocity-time graph equal to?

A

displacement

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14
Q

what’s the equation for force?

A

f=ma

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15
Q

what’s the equation for momentum?

A

m=mv

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16
Q

what’s the equation for work done?

A

work done = force x distance

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17
Q

what’s the equation for power?

A

power=work done/time

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18
Q

why do magnetism, gravity and electrostatics forces happen?

A

due to magnets, masses and charges interacting in fields

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19
Q

what’s a normal contact force?

A

it is the reaction force exerted at right angles to a surface in response to an object at rest exerting a force

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20
Q

what’s newton’s first law?

A

an object will continue to stay at rest or move at a uniform velocity unless a force acts on it.t

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21
Q

what’s newton’s first law aka?

A

law of inertia

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22
Q

what can a non-zero resultant force cause the object to do?

A

accelerate in the direction of the force

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23
Q

what does a steady speed mean about the force?

A

no resultant force

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24
Q

what is inertia a measure of?

A

how difficult it is to change the velocity of an object

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25
what’s inertial mass?
ratio of force over acceleration
26
which forces act on a parachutist at terminal velocity?
drag (air resistance) and gravity
27
why are parachutes helpful?
they allow you to reach a new LOWER terminal velocity
28
what will an object with 0 resultant force on it be doing?
stationary or travelling at a steady speed
29
what will an object w a non resultant force be doing?
accelerating/decelerating
30
why do you accelerate when you skydive?
earth exerts a larger force on you than the air
31
when skydiving, what’s the speed like when driving force = friction force?
steady
32
after just setting off when skydiving, why does acceleration eventually reduce until friction=driving force?
air resistance is proportional to velocity, so as velocity increases when you first set off, air resistance does too until they even out. there’s now no resultant force, and the object has reached its terminal velocity
33
how do parachutes help you reach a NEW terminal velocity?
when parachute opens, initially weight is less than air resistance force, but because velocity and air resistance are proportional, as velocity decreases so does air resistance, until weight=air resistance force. this is a new TV
34
what’s newton’s second law?
acceleration produced depends on size of force and mass of object (f=ma)
35
what’s momentum?
mass in motion : a vector quantity formed by multiplying mass x velocity
36
what’s the equation for force using m?
f=change in momentum / time
37
what’s the law of conservation of momentum?
momentum is conserved, so m before=m after
38
how many nm in 1 joule?
1
39
define power
rate of energy transfer
40
what’s newton’s third law?
for every action, there’s an equal and opposite reaction (forces come in pairs)
41
what does newton’s third law indicate about forces?
each force acts on a dif object, forces are the same size and type, forces act in opposite directions
42
why does an object moving in a circle with a constant velocity have a changing velocity?
velocity is a vector that has time and direction, and when moving in a circle your direction is constantly changing so velocity changes.
43
formula for force exerted by a spring
f= spring constant x extension (f=ke)
44
what’s the formula for weight (gravitational force)?
w=mg
45
what’s the formula for gravitational potential energy?
gravitation potential energy=mgh
46
whats the formula for pressure?
force/area
47
how do u calculate moment of a force?
moment= force x distance
48
what has to happen for an object to stretch, bend or be compressed?
more than 1 force needs to be applied
49
what’s the difference between elastic and plastic deformations (distortions)?
elastic deformations will return to their original shape, plastic won’t
50
what’s the relationship between force and extension for a SPRING?
directly proportional , linear until limit of proportionality
51
when is there a non linear relationship between force and extension?
when the object doesn’t obey hooke’s law
52
what is common with all matter?
all matter has a gravitational field that causes attraction
53
which objects is gravitational field strength stronger in?
more massive objects (more mass)
54
what is weight?
force acting on an object due to gravity
55
what’s the relationship between the weight of an object and the gravitational field strength?
a greater g means a greater weight
56
what’s the value of g on earth?
10 N/kg
57
what’s the acceleration in free fall?
10 N/kg
58
what’s the moment of a force?
turning effect of a force
59
what’s the principle of moments?
an object is balanced if anticlockwise moments=clockwise moments about the pivot
60
what’s a lever?
a force multiplier which transmits forces by rotating about a pivot
61
how do levers transmit forces?
increase the distance from the pivot where the force is applied, so less input force is needed for the same moment
62
how do hydraulic systems work?
a liquid to transmit a force: usually made of 2 pistons connected by a pipe - when u push 1 piston, pressure is transmitted through the liquid and the other piston moves
63
why are hydraulic systems possible using liquids?
liquids are incompressible, so if a force is applied to 1 point in a liquid there'll be a net force transmitted to other points (liquid pressure is the same everywhere)