Question

L. Ram avels on a straight road. He goes from position A to position B. The distance between A and B is
km. Now from position B he turns back and travels a distance of 2 km to reach the position C. Find
the total distance travelled by Ram during the whole journey and (ii) magnitude of his displacement
(Ans. Distance - 6 km; displacement - 2 km.​

Answer 1

CORRECT QUESTION:

Ram travels on a straight road. He goes from position A to position B. The distance between A and B is  2 km. Now from position B he turns back and travels a distance of 4 km to reach the position C. Find  (i) the total distance travelled by Ram during the whole journey and (ii) magnitude of his displacement.

DIAGRAM:

$\setlength{\unitlength}{1cm}\begin{picture}(1,0)\thicklines\put(0,0){\vector(1,0){2}}\thicklines\put(0,0){\vector(-1,0){2}}\put(0,0.1){ \bf A }\put(2,0.1){ \bf B }\put(-2,0.1){ \bf C }\put(0,-0.3){ \bold{ \underbrace{\qquad\qquad \qquad} }}\put(3.4,-0.3){ \bold{ \underbrace{\qquad\qquad \qquad} }}\put(4.2,-0.8){ \bf 2 m }\put(6.3,-0.8){ \bf 2 m }\put(5.7,0){\circle*{0.1}}\end{picture}$

ANSWER:

• (i) The total distance travelled = 6 km

• (ii) The magnitude of his displacement = - 2 km

GIVEN:

• Ram travels on a straight road.

• The distance between A and B is  2 km. Now from position B he turns back and travels a distance of 4 km to reach the position C.

TO FIND:

• (i) The total distance travelled by Ram during the whole journey.

• (ii) The magnitude of his displacement.

EXPLANATION:

(i) The total distance travelled by Ram during the whole journey:

Distance is the actual path length traversed by the body.

From A to B the distance travelled = 2 km

From B to C the distance travelled = 4 km

Total distance = Distance from A to B +  Distance from B to C.

Total distance = 2 + 4

Total distance = 6 km

Distance cannot be negative because it is a scalar.

(ii) The magnitude of his displacement:

Displacement is the shortest distance between the two points.

Displacement from A to B = 2 km

Displacement from B to C = - 4 km [Since it is opposite direction from A to B]

Total displacement = displacement from A to B +  displacement from B to C.

Total displacement = 2 - 4

Total displacement = - 2 km.

Displacement can be negative because displacement is a vector.