Speed, Displacement and Velocity
What is the difference between speed and velocity?
Speed is a scalar and tells us how fast an object is moving. Velocity is a vector and includes both magnitude and direction.
What is acceleration?
The rate of change of velocity.
or
Labelled formula
Which of the following is a vector quantity: mass, speed, temperature or velocity?
Velocity
What is Newton's First Law?
An object remains at rest or moves with constant velocity unless acted upon by a resultant external force
Why does a footballer wear studs on their boots?
The studs increase friction/grip between the boot and the ground, reducing slipping.
A car travels 150 m in 10 seconds. What is its average speed?
15 m/s
What does it mean if an object has zero acceleration?
Its velocity is constant. This means its speed and direction are not changing.
What is a scalar quantity?
A physical quantity with magnitude only.
What is meant by mass?
Mass is a measure of the amount of matter in an object
Why are cinema walls and ceilings covered in soft/absorbent materials?
To absorb sound, reducing reflections and echoes and improving the quality and clarity of the sound.
A student walks 50 m east and then 30 m west. What is their displacement?
20m east
What is the difference between positive and negative acceleration?
The sign of acceleration indicates its direction relative to the chosen positive direction.
What does the resultant vector represent when several vectors act on the same object?
The single vector that has the same effect as all the original vectors acting together.
Why don't the forces in a Newton's Third Law pair cancel each other out?
Because the two forces act on different objects.
Why does a falling object gain kinetic energy as it falls?
Its gravitational potential energy is transferred into kinetic energy as it falls.
What information can you get from a distance–time graph?
The slope represents speed. A steeper gradient means a greater speed, while a horizontal line represents an object at rest.
Can an object have a negative acceleration while still moving forwards? Explain.
Yes. If the object is moving in the positive direction but its acceleration is in the negative direction, its velocity is decreasing.
(For example, a car moving forwards while slowing down)
In the pulley experiment used to investigate vector addition, what is the purpose of the third force?
Put the object in equilibrium
What is meant by conservation of energy?
Energy cannot be created or destroyed, it can only be transferred from one form to another.
Why does a passenger move forwards when a car suddenly brakes?
Because of inertia. The passenger's body tends to continue moving with its original velocity while the car slows down.
A car travels around a circular track at constant speed. Is the car accelerating? Explain your answer.
Yes. Acceleration is the rate of change of velocity. Although the car's speed is constant, its direction of motion is continually changing, so its velocity is changing.
An object is moving at a constant velocity. What can you say about its acceleration and the resultant force acting on it? Explain.
Acceleration is 0 m/s2
FResultant = 0N
Why is it useful to resolve a vector into perpendicular components?
It allows a vector to be treated as separate components in independent directions, making problems involving forces or motion in two dimensions easier to analyse.
In the experiment investigating F=ma, why is it important to keep the total mass constant when investigating the relationship between force and acceleration?
Because we want to investigate the effect of force alone on acceleration.
If the mass also changed, we would not know whether a change in acceleration was caused by the change in force or the change in mass.
Why does a rocket move upwards when it ejects gases downwards?
The gases are accelerated downwards, giving them downward momentum. To conserve momentum, the rocket gains an equal change in momentum in the opposite direction.