Mark the correct statements for a particle moving along a straight line: a)if the velocity is 0 at an instant, the acceleration must be 0. b)if the velocity is 0 for a time interval, the acceleration is 0 at any instant within the time interval. c)if the velocity and acceleration have the opposite signs, the object slows down. Among the following, the correct statement is (multi or single option) a)If the acceleration of an object is constant,then it must move in a straight line. b)If the acceleration of an object is 0,then its speed remains constant. c)If the speed of an object remains constant then its acceleration must be 0.

CBSE Class 7 Answered

Mark the correct statements for a particle moving along a straight line:

a)if the velocity is 0 at an instant, the acceleration must be 0.

b)if the velocity is 0 for a time interval, the acceleration is 0 at any instant within the time interval.

c)if the velocity and acceleration have the opposite signs, the object slows down.

Among the following, the correct statement is (multi or single option)

a)If the acceleration of an object is constant,then it must move in a straight line.

b)If the acceleration of an object is 0,then its speed remains constant.

c)If the speed of an object remains constant then its acceleration must be 0.

Asked by jhilmilsoma | 29 Nov, 2015, 11:40: AM

Expert Answer

(a) False. Consider that a particle is thrown vertically upward. At its highest point, the velocity is zero but acceleration is not zero.

(b) Acceleration is defined as rate of change of velocity. If in a time interval velocity is zero, it means that in this interval the velocity does not change. So acceleration at any instant in this time interval is zero.

(c) True. If the acceleration and velocity of the particle have opposite sign it has a retarding effect. During retardation, acceleration opposes velocity.

Note: Kindly ask the other query as a separate question.

Answered by Faiza Lambe | 30 Nov, 2015, 09:22: AM