Linear motion is the motion in 1 dimension (1-D) or the motion in a straight line.
Distance
- The distance traveled by an object is the total length that is traveled by that object.
- Distance is a scalar quantity.
- The SI unit of distance is m (metre).
Displacement
- Displacement of an object from a point of reference, O is the shortest distance of the object from point O in a specific direction.
- Displacement is a vector quantity.
- The SI unit of displacement is m (metre).
Distance travelled = 200mDisplacement = 120 m, in the direction of Northeast
Speed
- Speed is the rate of change in distance. It is a measure of how fast the distance change in a movement.
- Speed is a scalar quantity.
- The SI unit of speed is m/s (metre per second)
Equation of Speed
Velocity
- Velocity is define as the rate of displacement change. It is the measure of how fast the displacement change of a moving object.
- Velocity is a vector quantity.
- The unit of displacemnet is m/s (metre per second)
Equation of velocity
Positive or Negative Sign of Velocity- In velocity, the positive/negative sign indicates direction.
- You can take any direction as positive and the opposite as negative.
- For a linear motion, normally we take the motion to the right as positive and hence the motion to the left as negative.
Acceleration is the rate of velocity change.Acceleration is a vector quantity. It is a measure of how fast the velocity change.
Acceleration is a vector quantity.
The unit of acceleration is ms-2.
Equation
Additional NotesAn object moves with a constant velocity if the magnitude and direction of the motion is always constant.
An object experiences changes in velocity if
- the magnitude of velocity changes
- the direction of the motion changes.
An object traveling with a constant acceleration, a, if the velocity changes at a constant rate.
Equation of Uniform Acceleration
Most of the motion problems can be solved by the following equations. Therefore, make sure that you memorise all of them.
How we know when to use the equation?
There are 3 types of motion:- motion with uniform velocity
- motion with uniform acceleration
- motion with changing acceleration
Motion with changing acceleration is not in SPM Physics syllabus. It will be discussed in Form 5 add maths.
Analysing Ticker Tape
Ticker Timer
A ticker-timer consists of an electrical vibrator which vibrates 50 times per second. This enables it to make 50 dots per second on a ticker-tape being pulled through it. The time interval between two adjacent dots on the ticker-tape is called one tick. One tick is equal to 1/50 s or 0.02 s.
Uniform Velocity
The distance of the dots is equally distributed.- All lengths of tape in the chart are of equal length.
- The object is moving at a uniform velocity.
Uniform Acceleration
The distance between the dots increases uniformly.- The length of the strips of tape in the chart increase uniformly.
- The velocity of the object is increasing uniformly, i.e. the object is moving at a constant acceleration.
The distance between the dots decreases uniformly.- The length of the strips of tape in the chart decreases uniformly.
- The velocity of the object is decreasing uniformly, i.e. the object is decelerating uniformly.
Finding Velocity
Velocity of a motion can be determined by using ticker tape through the following equation:
Caution!:
t is time taken from the first dot to the last dot of the distance measured.
Example 1
Diagram 2.4 shows a strip of ticker tape that was pulled through a ticker tape timer that vibrated at 50 times a second. What is the
a. time taken from the first dot to the last dot?
b. average velocity of the object that is represented by the ticker tape?
Answer:
a. There are 15 ticks from the first dot to the last dot, hence
Time taken = 15 × 0.02s = 0.3s
b. Distance travelled = 15cmFinding Acceleration
Acceleration of a motion can be determined by using ticker tape through the following equation:
Caution!:
t is time taken from the initial velocity to the final velocity.
