Read each statement below carefully and state with reasons and examples if it is true or false ;
A particle in one-dimensional motion
(a) with zero speed at an instant may have non-zero acceleration at that instant
(b) with zero speed may have non-zero velocity,
(c) with constant speed must have zero acceleration,
(d) with positive value of acceleration must be speeding up.
a) True
b) False
c) True
d) False
Explanation:
(a) When a body is thrown vertically upwards in the space, then at the highest point, the body has zero speed but has downward acceleration equal to the acceleration due to gravity.
(b) Because velocity is the speed of the body in a given direction. When speed is zero, the magnitude of the velocity of the body is zero, hence velocity is zero.
(c) When a particle is moving along a straight line with a constant speed, its velocity remains constant with time.
Therefore, acceleration ( change in velocity/time) is zero.
(d) If the position direction is not along the direction of motion the object is not speeding up.
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