CBSE Class 9 Science Force and Laws of Motion Worksheet Set B

Short Answer

Question. An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Answer : Yes,an object can have zero displacement even when it has moved through a distance.This happens when final position of the object coincides with its initial position. For example,if a person moves around park and stands on place from where he started then here displacement will be zero.

Question. Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object.
Answer : None of the statement is true for displacement First statement is false because displacement can be zero. Second statement is also false because displacement is less than or equal to the distance travelled by the object.

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, only when an object is moving in a straight line.

Question. What does the path of an object look like when it is in uniform motion?
Answer : An object having uniform motion has a straight line path.

Question. When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Answer :
(i) A body is said to be in uniform acceleration if it travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time.
(ii) A body is said to be in nonuniform acceleration if the rate of change of its velocity is not constant.

Question. A train starting from a railway station and moving with uniform acceleration attains a speed 40 km h−1 in 10 minutes. Find its acceleration.
Answer :