Chapter 2: Motion in One Dimension

Scalar Quantities

Physical quantities that are expressed only by their magnitude.

Vector Quantities

Physical quantities that are expressed by both magnitude and direction.

Distance

The total length of the path through which a body has moved.

Displacement

The shortest distance from the initial to the final position of a body, including direction.

Speed

The rate of change of distance with time; a scalar quantity.

Velocity

The distance travelled per second by the body in a specified direction; a vector quantity.

Acceleration

The rate of change of velocity with time.

Retardation

A negative acceleration; when a body slows down.

Uniform Speed

Covers equal distances with equal amounts of time.

Instantaneous Speed

The speed of an object at a specific instant in time; a ratio of the distance travelled in very short interval of time to the time interval.

Average Speed

The total distance traveled divided by the total time taken.

Uniformly Accelerated Motion

Motion in which the velocity of an object changes at a constant rate.

Rest

An object is at rest if it does not change its position with respect to its surroundings.

Positive Acceleration

An increase in velocity over time.

Free Fall

The motion of a body when gravity is the only force acting upon it.

Average Velocity

The total displacement divided by the total time taken.

Instantaneous Velocity

The velocity of an object at a specific moment in time.

One-Dimensional Motion

Motion that occurs along a straight line.

Differentiate between Distance and Displacement

• The magnitude of distance is either equal to or less than distance.

• Distance is always positive, but displacement can be negative.

• Displacement can be 0 even if distance is not.

Variable Speed

Covers unequal distances in equal intervals of time or Vice Versa.

Uniform Velocity

A body travelling equal distances in equal intervals of time in a particular direction.

Variable Velocity

A body moving equal distances in unequal intervals of time in different directions or vice versa.

Retardation

Decrease of velocity with time.

Variable acceleration

A change in velocity over time that is not same in same intervals of time .

Acceleration due to Gravity

When a body falls due to gravity, the acceleration produced in the body due to Earth’s gravitational attraction. Approx 9.8

Places where g is maximum

At the poles and on the surface.

Places where g is minimum

At the equator and the centre of the Earth.

Example of Uniform Speed

A ball rolling on a frictionless plane surface

Example of Uniform Velocity

The rain drops falling from the sky

Examples of Variable Velocity

Motion of a body in circular path, Motion of free falling body.

Motion

A body changing its position with respect to its immediate surroundings.

Displacement time graph is a straight line

Object is stationary

Displacement graph is a straight line inclined to time axis

Body is moving with uniform velocity

Displacement time graph is a curve

Body moving with non uniform velocity

Quantities u can find in displacement time graph

Velocity by calculating the slope of the straight line

Velocity time graph can never be a straight line parallel to the velocity axis

It would mean that velocity increases without increase in time which is impossible.

Velocity time graph is a straight line parallel to the time axis

Motion of uniform velocity

Velocity-time graph is straight line inclined to time axis

Motion of uniform acceleration

Velocity time graph is a curve

Motion of non uniform acceleration

Quantities u can find in velocity time graph

Acceleration (Slope), Displacement and distance ( area of graph)

Acceleration time graph is a line coinciding with time axis

The body is stationary

Acceleration time graph is a straight line parallel to time axis

Motion of uniform acceleration

Acceleration time graph is a curve

Motion of variable acceleration

Acceleration time graph is a straight line parallel to the time axis on the negative side of the acceleration axis

Motion of uniform retardation

Velocity time graph of free falling body

Straight line inclined to time axis

Displacement time graph of free falling body

It is a curve