## Motion in a Straight Line

A body is said to be in motion if it changes its position with respect to time.

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**See Also:** Important Questions: Motion in a straight line

### Types of Rectilinear/Linear Motion

The Rectilinear Motion or linear motion can be of two types:

- Non-Uniform linear motion with non-zero acceleration orÂ variable velocity
- Uniform linear motion with zero acceleration or constant velocity

The simplest type of one-dimensional motion is Linear motion. As perÂ Newtonâ€™s first law of motion, an object will either be in rest or continue to move in a straight line with a uniform velocity unless and until an external force is applied to it.

Linear motion is often mistaken for general motion. Linear motion is a one-dimensional motion but in general, the motion has both magnitude and direction, i.e. an objectâ€™s position and velocity are described inÂ vector quantities.

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### Uniform Motion in a Straight Line

A body is said to be in a uniform motion if it travels in a straight line covering equal distances in equal intervals of time. A body is said to have uniform acceleration if the rate of change of its velocity remains constant.

*The ball covers equal distances in equal intervals of time***Example:**

If a car travels at a speed of 60 km/hour then it will cover a distance of 1 km/minute. In this sense, the motion of car acceleration is uniform.

#### For More Information On Motion in One Dimension, Watch The Below Video:

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### Non-uniform Motion in a Straight Line

A body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. While in movement, the rate of change of its velocity changes at different points of time.

**Example:**

A boy kicking a football. It might cover 4 meters in the first attempt, 6 meters in the second change, 9 meters in the third attempt and so on as per the velocity exerted by the boy.

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### Path Length

The path length is the total length of the path that has to be traversed by the object.

### Displacement

Displacement is the change in position of a body. The magnitude of displacement between the same points is proportional to the path length.

To get more details on Displacement Formula, visit here.

### Uniform Motion

When the displacement of an object is equal in equal time intervals, the motion is said to be uniform, else it is referred to as non-uniform.

### Average Speed

Average speed is referred to the ratio between the total path length traversed to the time taken.

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### Instantaneous Velocity

It is the velocity when the limit of the average velocity has an indefinitely smaller interval of time.

To get more details on Instantaneous Velocity Formula, visit here.

### Average Acceleration

It is the change in velocity corresponding to the time interval with in which the change has accelerated.

Also AccessÂ |

NCERT Solutions for class 11 Physics Chapter 3 |

NCERT Exemplar for class 11 Physics Chapter 3 |

### Important Questions

- 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

- 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)

Visit the links below to get the class 11 physics chapter 3 (Motion in a Straight Line) notes. Motion in a Straight Line NCERT Solution Motion in a Straight Line

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