Chapter 2 Kinematics Flashcards
Define scalar quantities.
Scalar quantities are physical quantities that have magnitude only. Examples include distance, speed and time.
Define vector quantities.
Vector quantities are physical quantities that have both magnitude and direction. Examples include displacement, velocity and acceleration.
What are the differences between distance and displacement?
Distance:
- The total length covered by a moving object regardless of the direction of motion
- A scalar quantity (i.e. has magnitude only)
- Always increases
Displacement:
- The distance measured in a straight line in a specified direction.
- A vector quantity (i.e. has both magnitude and direction)
- Always measured from a specific reference point
- Can be positive or negative, depending on the position of the object from the reference point
Define speed.
Speed is the distance moved per unit time.
Define instantaneous speed.
The speed of an object at a particular instant.
Define velocity.
Velocity is the rate of change of displacement.
Define average speed and the assumption made to calculate it.
Average speed is the total distance travelled per unit time. Assume that the object travels at the same speed throughout the entire distance.
Define average velocity and the assumption made to calculate it.
Average velocity is the total displacement travelled per unit time. Assume that the object travels at the same velocity throughout the entire journey.
Define acceleration.
Acceleration is the rate of change of velocity.
When does an object undergo deceleration?
When the velocity of an object decreases over time, it undergoes deceleration.
Define uniform acceleration.
Uniform acceleration is the constant rate of change of velocity.
When does an object undergo uniform acceleration?
An object undergoes uniform acceleration when the change (increase/ decrease) in its velocity for every unit of time is the same, i.e. the rate of change of velocity is constant.
When does an object undergo non-uniform acceleration?
An object undergoes non-uniform acceleration if the change in its velocity for every unit of time is not the same.
How do we calculate the total displacement using a velocity-time graph?
Calculate the total area under the velocity-time graph, which gives the total displacement
Describe speed in the following scenarios:
1) +ve velocity, +ve acceleration
2) +ve velocity, -ve acceleration
3) -ve velocity, -ve acceleration
4) -ve velocity, +ve acceleration
1) Speeding up in the positive direction (e.g. speeding up while running)
2) Slowing down to zero speed (e.g. slowing down to stop at a red light)
3) Speeding up in the negative direction (e.g. dropping an object from a height, taking upwards as positive)
4) Slowing down to zero speed
Explain:
1) Positive acceleration
2) Negative acceleration
3) Deceleration
1) Acceleration in the positive direction
2) Acceleration in the negative direction
3) Negative acceleration with decreasing speed
a) Displacement-time graph with constant gradient gives: __________
b) Displacement-time graph with non-uniform gradient gives: __________
1) Displacement-time graph with constant gradient gives velocity of the object
b) Displacement-time graph with non-uniform gradient: gradient of tangent is equal to the instantaneous velocity of the object at that instant
Given a speed-time graph, what does the area under the graph give?
Area under speed-time graph = distance travelled by object
Negative gradient = object moving towards observer
True or false?
False.
Negative gradient ≠ object moving towards observer.
Displacement approaching zero either from +ve or -ve direction = object moving towards observer
Given a velocity-time graph, what does the
a) Gradient
b) Area under graph
give?
a) Gradient of the velocity-time graph = acceleration of the object.
b) Area under the velocity-time graph = total displacement of the object
a) Velocity-time graph with constant gradient gives: __________
b) Velocity-time graph with non-uniform gradient gives: __________
a) Velocity-time graph with constant gradient gives acceleration of the object
b) Velocity-time graph with non-uniform gradient: gradient of tangent is equal to the instantaneous acceleration of the object at that instant
What is the acceleration due to gravity?
It is a constant that is approximately 10 m/s² (i.e. steadily increasing velocity)
When does an object experience acceleration due to gravity?
When does an object experience acceleration due to gravity?
What is free-fall?
Free-fall is the motion of objects that move under the sole influence of gravity; free-falling objects do not encounter air resistance.
