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science eoy > motion & forces > Flashcards

motion & forces Flashcards

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1
Q

what’s the difference between distance and displacement

A 
distance = how far an object moves, scalar quantity
displacement =  the distance an object moves in a straight line from the starting point to the finishing point, vector quantity
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2
Q

is velocity scalar or vector

A

vector - has both magnitude and direction

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3
Q

name some scalar quantities

A

mass, energy, temperature, speed, distance

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4
Q

name some vector quantities

A

force, velocity, acceleration, momentum, displacement

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5
Q

if a car travelling at +10m/s suddenly turns around and continues at the same speed, what is its new velocity

A

-10m/s

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6
Q

what is momentum

A

a combination of mass and velocity, it is a vector quantity

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7
Q

how do you calculate speed

A

speed = distance / time taken

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8
Q

how do you calculate speed from a distance/time graph

A

speed = gradient of the line

distance/time taken

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9
Q

on a speed/time graph, what does the gradient mean

A

acceleration

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10
Q

how do you find the distance travelled from a velocity/time graph

A

the area under the line

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11
Q

what are light gates used for

A

to see how long it takes an object to pass through them, you calculate the speed using v = x / t
(x is the length of the object)

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12
Q

what is the equation for acceleration

A

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

a = v^2 - u^2 / t

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13
Q

what’s the equation for final speed

A

initial speed + (acceleration x time)

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14
Q

how do you calculate final velocity

A

v^2 - u^2 = 2ax

x = distance

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15
Q

if an object decelerates, how would you write the acceleration of it

A

a negative number m/s^2

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16
Q

what is the acceleration due to gravity

A

9.8 m/s^2

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17
Q

how could there be a change in velocity but not a change in speed

A

if an object is travelling at a constant speed but is also changing direction

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18
Q

what is a resultant force

A

the sum of all forces acting on an object, if the forces acting on an object are unbalanced then there is a resultant force acting on the object
it will always act towards the centre of the circle if moving in a circular motion

19
Q

what is the equation for resultant force

A

resultant force = forces acting in one direction - forces acting in the opposite direction

20
Q

what is newton’s first law

A

that the velocity of an object will only change if a resultant force is acting on the object

21
Q

what is newton’s third law

A

when 2 objects interact, the forces they exert on each other are equal and opposite

22
Q

how do you calculate force

A

mass x acceleration

23
Q

how do you calculate momentum

A

mass x velocity

24
Q

what is the law of conservation of momentum

A

momentum cannot be created or destroyed

25
Q

how do you calculate change in momentum

A

mv - mu

m = mass) (v = final velocity) (u = initial velocity

26
Q

force = rate of what?

A

change in momentum

27
Q

what do crumple zones in cars do

A

absorb the kinetic energy transferred by collisions, they increase the time taken for the change in momentum to happen, this reduces the force experienced by the driver

28
Q

what is inertia

A

how difficult it is to change the objects motion

29
Q

what is the equation for weight

A

mass x gravitational field strength

30
Q

what is weight measured in

A

newtons (N)

31
Q

how do you calculate mass

A

weight / gravitational field strength

32
Q

what is air resistance

A

a frictional force that opposes the motion of objects moving quickly through air
the force due to air resistance increases as the speed of the falling object increases

33
Q

what factors affect a driver’s thinking distance

A

tiredness, alcohol or drugs, distractions

34
Q

what factors affect the car’s braking distance

A

condition of the car, road conditions, initial car speed

35
Q

what is stopping distance

A

thinking distance + braking distance

36
Q

what is a typical reaction time for humans

A

0.25 seconds

37
Q

how do you convert 50 km/h to m/s

A

50 x 1000 m/h
(50 x 1000) / 3600s
50 km/h = 13.9 m/s

38
Q

what is the typical speed of walking and sound

A 
walking = 1.4m/s
sound = 340m/s
39
Q

how do you calculate work done

A

force x distance moved in the direction of the force

40
Q

how do you calculate kinetic energy

A

0.5 x mass x velocity^2

41
Q

work done =

A

initial kinetic energy

42
Q

what are some dangers of large decelerations

A

brakes could overheat, the car could skid

43
Q

the greater the braking force the ______ the deceleration of the vehicle

A

greater

44
Q

how do you calculate braking force

A

deceleration x mass

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