 # Class 11 Physics Chapter 3 Notes Motion In A Straight Line

## What is Motion in a Straight Line?

If the position of an object changes with time then it is said to be in motion.

### What is Path Length?

The total length of the path which has to be traversed by the object is known as path length.

### What is Displacement?

The change in position is termed as displacement. The displacement magnitude between the same points is proportional to path length.

### What is Uniform Motion?

When the object’s displacement is equal in equal intervals of time, then it is called uniform otherwise is referred to as non-uniform.

### What is Average Speed?

The ratio between total path length traversed and the time has taken is called average speed.

### What is Instantaneous Velocity?

Whenever the limit of average velocity has an infinitely small time interval, then it is referred to as instantaneous velocity.

### What is Average Acceleration?

The change in velocity with respect to the time interval within which the change happened is termed as average acceleration.

### Important Questions

1. In which of the following examples of motion, can the body be considered approximately a point object:
• (a) a tumbling beaker that has slipped off the edge of a table
• (b) a monkey sitting on top of a man cycling smoothly on a circular track.
• (c) a railway carriage moving without jerks between two stations.(d)a spinning cricket ball that turns sharply on hitting the ground
1. The position-time (x-t) graphs for two children A and B returning from their school O to their homes P and Q respectively are shown in Fig. 3.19. Choose the correct entries in the brackets below ;
• (a) (A/B) lives closer to the school than (B/A)
• (b) (A/B) overtakes (B/A) on the road (once/twice)
• (c) (A/B) walks faster than (B/A)
• (d) A and B reach home at the (same/different) time
• (e) (A/B) starts from the school earlier than (B/A)

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