Wednesday , July 6 2022 # 9th Class (CBSE) Science: Motion

#### Question: An object has move through a distance. Can it has zero displacement? If yes, support your answer with example.

Answer: Yes the object inspite of moving through a distance can have zero displacement. Example, if an object travels from point ‘A’ and reaches to the same point ‘A’, then its displacement is ‘O’.

#### Question: A farmer moves along the boundary of a square field of side 10m in 40s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position?

Total distance = 40m
Time taken = 40s
∴ Total time taken by the farmer = 2 min 20 seconds = 140 seconds
∴ 140 ÷ 40 = 3.5
∴ The farmer completes 3 and a half round of the square. i.e., if he starts from A he reaches point ‘C‘ after 2 minutes 20 seconds.
∴ Displacement is AC.

To find AC, assume ΔADC (right angle triangle) ∴ AC2 = (10)2 + (10)2
AC2100 +100
AC2200
∴ AC = 10√2m

#### Question: Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?

Answer: The magnitude of average velocity of an object is equal to its average speed if the object moves in a straight line in a particular direction.

#### Question: What dose the path of an object look like when it is in uniform motion?

Answer: It is a straight line.

#### Question: What does the odometer of an automobile measure?

Answer: The odometer of an automobile measure the distance traveled by a vehicle.

#### Question: During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is 3 × 108 ms-1.

Time taken = 5 minutes = 5 × 60 sec = 300 sec
Speed of signal u = 3 × 108 m/s
Distance = ?
Speed = distance / time
∴ distance = speed × time
∴ Distance = 3 × 108 300
= 9 × 108 m.

#### Question: When will you say a body is in

1. Uniform acceleration and
2. Non-uniform acceleration?