SUBJECT : PHYSICSUNIT : DISTANCE & DISPLACEMENTGRADE : VIII

SUBMITTED BYGOPAKUMAR K.

B.Ed (PHYSICAL SCIENCE)RAJEEV MEMORIAL COLLEGE OF TEACHER

EDUCATION

MOTION

The change in position of a body with time is motion.

Motion can be described in terms of the distance moved or displacement.

B

A C Distance is the actual length of the path travelled by a body. In the figure distance travelled is length of path from A to B and from B to C.

Displacement is the length of the shortest path travelled by a body from its initial position to its final position. Displacement as per above figure is length of the path from A to C.

0 5 10 15 20 25 30 35 40 45 50 55 60 km

O C B A

If a body starts moving in a straight line from origin O and moves through C and B and reaches A and then moves back and reaches C through B, then Distance travelled = 60 + 35 = 95 km Displacement = 25 km

Displacement Vs Distance

displa

cemen

t

distance

Stopped here

• Even though the Physics teacher has walked a total distance of 12 meters, the displacement is 0 meters.

• During the course of her motion, she has "covered 12 meters of ground" (distance = 12 m).

A Physics teacher walks 4 meters East, 2 meters South, 4 meters West, and finally 2 meters North.

Distance is a scalar quantity. It has only magnitude.

Displacement, however, is a vector quantity and has magnitude as well as direction.

The SI unit for measuring distance is the meter (m).

For very large distances, it is more common to make measurements in kilometer (km).

Distances that are smaller than a meter are measured in centimeter (cm).

Review

_______________ is the actual length of the path described by a body in motion.

The straight line or shortest distance between the initial position and final position of a body is _______________.

Distance is a ____________ quantity, has only _____________.

Displacement is a ___________ quantity, has both magnitude and _____________.

Distance

Displacement

scalar magnitude

vectordirection

Review B 12m C

10m 15m 11m

A 18m D

Complete the table on the basis of the figureInstance Distance DisplacementA to BA to C (via B)A to D (via B & C)

10m

10m22

m15m33

m18m