Topic 1 & 2 Forces & Motion Flashcards
Runner A finishes a race in less time than runner B. Who is faster?
Runner A
What two measurements are needed to calculate speed?
distance and time
What is the SI unit for speed?
m/s
What does acceleration mean?
speeding up or slowing down
What is a force?
push or pull
How do we represent forces on diagrams?
arrows, with length depending on size of force
What does mass mean?
amount of substance
What is the unit for mass?
kilogram
What does a vector have that a scalar does not?
direction
Name a scalar and a vector measured in metres.
distance, displacement
Name a scalar and a vector measured in metres/second.
speed, velocity
Name a vector with units of newtons.
force or weight
Is mass a vector or scalar?
scalar
Is energy a vector or scalar?
scalar
What is acceleration?
a change in velocity
Why is acceleration a vector?
it is measuring a change in another vector
What is the difference between speed and velocity?
velocity has a direction/is a vector
What is the equation for calculating speed?
speed = distance / time
What is the SI unit for speed?
metres per second
What is the equation for average speed?
total distance / time for whole journey
What is the equation for calculating distance?
distance = speed x time
How is a constant speed shown on a distance/time graph?
straight, sloping line
What does a horizontal line on a distance/time graph show?
stationary object
What is the speed of sound in air?
approximately 330m/s
How is a stationary object shown on a distance/time graph?
horizontal line
How can you tell which part of a journey shown on a distance/time graph has the highest speed?
steepest line
How can you calculate velocity from a distance/time graph?
gradient of line
What does acceleration mean?
change in velocity in time
What are the units for acceleration?
metres per second squared
In the acceleration equation, what does u stand for?
initial velocity
In the acceleration equation, what does v stand for?
final velocity
What is the equation for calculating acceleration?
change in velocity/time
What is the acceleration due to gravity?
10m/s2 to 1 sig. fig or 9.8m/s2 to 2 sig. fig.
What is the force that pulls us towards the Earth?
gravity
What is ‘drag’ another name for?
air resistance or water resistance
What are balanced forces?
forces of the same size in opposite directions
What do we call the forwards force produced by an aeroplane’s engine or propeller?
thrust
What word describes both the speed and direction of movement of an object?
velocity
What is the name for a single force on an object with the same effect as all the forces combined?
resultant
How do we describe the forces on an object when the force in one direction is bigger than the force in the other?
unbalanced
Two forces on an object are in the same direction. How do we calculate the resultant force?
add
Two forces on an object are in opposite directions. How do we calculate the resultant force?
find the difference between them
What does the length of a force arrow on a diagram represent?
size of force
An aeroplane has thrust of 2000N and drag of 1800N. What is the resultant?
200N forwards
Air resistance on a cyclist is 20N and friction is 5N. What is the total force trying to slow the cyclist down?
25N backwards
Name a vector quantity that changes as a car drives at constant speed around a roundabout.
velocity
What are unbalanced forces?
forces of different sizes in opposite directions
What is the direction of the resultant force on a car that is speeding up?
forwards
What is the direction of the resultant force on a bicycle that is slowing down?
backwards
How does a sideways resultant force affect the velocity of a moving object?
changes its direction
How can the pilot of an aeroplane make the plane gain speed upwards?
increase the lift/upwards force
How do balanced forces affect the velocity of a moving car?
The car continues with the same velocity.
You pedal harder on a bicycle. What happens?
you accelerate/get faster
What is the name of the force that makes objects move in a circular path?
centripetal
What provides the centripetal force for a car going around a roundabout?
friction
What are the forces on a moon orbiting around a planet?
gravity acting towards the planet
In which direction does centripetal force act?
towards the centre of the circle .
Why is the force of gravity greater on a lorry than on a car?
larger mass
Why is the resultant force accelerating a car usually less than the force provided by its engine?
air resistance and/or friction
Name one force that usually has to be taken into account when working out the resultant force on a moving object
drag or friction
When will a resultant force act to slow a car down?
when backwards forces are greater than forwards ones
How can friction act to make a car speed up?
between tyres and road
How can friction act to make a car slow down?
in brakes
What is the formula linking force, mass and acceleration?
F = m x a
An object is moving at a constant velocity. What can you say about the forces on it?
balanced
What is the equation relating to constant velocity?
speed = distance / time
What type of force is used to slow down a moving vehicle?
friction
Where is this force applied?
brakes, tyres
Why is a wet road more slippery than a dry one?
water acts as lubricant
An object has a negative acceleration. What does this mean?
it is slowing down
What effect does drinking alcohol have on human reaction times?
slows them down/makes them longer
How will being tired affect reaction time?
make it longer
What does braking distance mean?
the distance a car travels while slowing down
What does thinking distance mean?
the distance a car travels while the driver is reacting to a danger and deciding to apply the brakes
How does speed affect the thinking distance?
higher speed, longer thinking distance/thinking distance directly proportional to speed
How does speed affect the braking distance?
higher speed, longer braking distance/braking distance proportional to speed squared
How does the force needed for an acceleration depend on the size of the acceleration?
larger acceleration, larger force needed
What does deceleration mean?
slowing down/a negative acceleration
What factors affect the momentum of a moving object?
mass, velocity
How does the mass affect momentum?
higher mass, higher momentum
How does the velocity affect momentum?
higher velocity, higher momentum
What does momentum is conserved mean?
total momentum is the same before and after a collision
