Motion Along a Straight Line

What is the shortest distance measured from the initial to the final position of an object known as?

Can the magnitude of the displacement be equal to the distance travelled by an object?

What is the magnitude of displacement from O to A and back to B in Fig. 8.1?

What is the total distance covered by the object in its motion from O to A and back to B?

What is the displacement of the object when it travels back to its initial position O?

What is the total distance covered by the object when it travels from O to A and back to O?

What is the simplest type of motion?

What is the reference point of an object's motion in Fig. 8.1?

What is the difference between distance and displacement?

What is the purpose of an odometer in an automobile?

What is the magnitude of the displacement between Bhubaneshwar and New Delhi?

What is the total distance covered by the object in the given example?

What is the numerical value of a physical quantity called?

What can you find out by subtracting the initial position from the final position?

Motion Along a Straight Line

Motion along a straight line is the simplest type of motion.
The object starts its journey from a reference point O and moves along a straight path.
The position of the object at different instants is represented by A, B, and C.
Displacement and distance are used to describe the overall motion of an object and to locate its final position with reference to its initial position at a given time.

Distance and Displacement

Distance is the total path length covered by an object.
Distance is measured by specifying only its numerical value and not the direction of motion.
The magnitude of displacement is the shortest distance measured from the initial to the final position of an object.
Displacement is a directed quantity and has both magnitude and direction.

Example and Activity

Consider the motion of an object moving from O to A, then back to B, and finally to C.
The distance covered by the object is OA + AC = 60 km + 35 km = 95 km.
The magnitude of displacement from O to C is the shortest distance, which is 35 km.
The magnitude of displacement is not equal to the distance travelled by an object.
Activity 8.3: Measure the distance covered by walking along the sides of a basket-ball court and compare it with the magnitude of displacement.

Odometer and Displacement

An odometer is a device that shows the distance travelled by an automobile.
The difference between the final and initial readings of the odometer gives the magnitude of the displacement between two points.

Key Points

The magnitude of displacement can be zero, but the corresponding distance covered is not zero.
The distance covered in a journey may not be equal to the magnitude of displacement.

Learn about the simplest type of motion, describing an object's movement along a straight path, with reference points and positions at different instants.