Motion Flashcards
What is a scalar quantity?
● A quantity that only has a magnitude
but no direction
What is a vector quantity?
A quantity that has both a magnitude and a direction.
How can a vector quantity be represented?
Using vector arrows.
How do vector arrows represent vectors?
● The length of the arrow represents the
magnitude
● The arrow points in the associated
direction
Give examples of vector quantities.
- Velocity
- Displacement
- Force
- Weight
- Acceleration
What is velocity?
The speed of an object in a specific direction.
Give examples of scalar quantities.
● Temperature
● Time
● Mass
● Speed
● Distance
● Energy
On a distance/time graph, what value does the gradient of the line represent?s
speed
Give an equation relating average speed, distance and time.
average speed = distance / time
On a displacement/time graph, what value does the gradient of the line represent?
velocity
What must be done to calculate speed at a given time from a distance-time graph for an accelerating object?
● Draw a tangent to the curve at the required time
● Calculate the gradient of the tangent
State the equation for the average acceleration of an object. Give appropriate units.
Acceleration = (v-u)/t
Acceleration (m/s²), Velocity (m/s), Time (s)
Give an equation relating final velocity with initial velocity, displacement and acceleration.
v2 = u2 + 2as
How can the distance travelled by an object be calculated from a velocity-time graph?
It is equal to the area under the graph.
On a velocity/time graph what does the gradient of the graph represent?
The acceleration.
State a typical value for the speed of sound.
330 m/s
Typical value for speed of light
3 x 10^8 m/s
What is a typical value for human walking speed?
1.5 m/s
What is a typical value for human running speed?
3 m/s
What is a typical value for human cycling speed?
6 m/s
Give an approximate value for the acceleration of an object in free fall under gravity near the Earth’s surface.
10 m/s²
Light gates experiment (5)
● Set up two, one at start and one at end
● Measure distance between them
● As soon as the object passes through the first, it will measure the time taken to reach the second
● Then use speed= distance/time
● This is more accurate as removes reaction time and human error with a stopwatch
How can you measure human reaction times?
● Using the ruler drop test
● Person A and B hold each end of a ruler with the 0 cm
mark at the bottom
● Person A drops the ruler without telling person B
● Person B catches it
● The distance travelled corresponds to their reaction
time
Why is it important that the 0cm mark is at the bottom?
So you can obtain the distance directly without having to calculate it; otherwise, a zero error would need to be accounted for.
What is the stopping distance of a vehicle equal to?
thinking distance + braking distance
For a given braking distance, if the vehicle’s speed is increased, what can be said about its stopping distance?
The stopping distance is increased with an increase in speed.
Give a typical range of values for human reaction time.
0.2 seconds - 0.9 seconds
Give three factors which can affect a driver’s reaction time.
- Tiredness
- Drugs
- Alcohol
Give two factors which may affect braking distance.
- Adverse (wet/icy) road conditions
- Poor tyre/brake conditions
Describe the energy transfers that take place when a car applies its brakes.
● Work is done by the friction force between the brakes and wheel
● Kinetic energy of the wheel is converted to heat and is dissipated to the surroundings
through the brake discs
To stop a car in a given distance, if its velocity is increased, what must happen to the braking force applied?
The braking force must also be increased.
State two consequences of a vehicle undergoing very large decelerations.
Kinetic energy converted to heat is very high causing brakes to overheat
2. Loss of control of the vehicle
