Question

Read each statement below carefully and state with reasons and examples, if it is true or false:A particle in one dimensional motiona. with zero speed instant may have non zero acceleration at that instantb. with zero speed may have non zero velocityc. with constant speed must have zero accelerationd. with positive value of acceleration must be speeding up

Answer 1

Hii dear,

# Answers-
a. True
b. False
c. True
d. False

# Explaination-
a. True.
For example, when body is protected vertically upwards at max height, it has zero velocity but non-zero acceleration.

b. False.
Magnitude of displacement is always lesser than or equal to total path length, hence at zero speed magnitude of velocity must be zero.

c. True.
Since, speed is constant, rate of change of velocity will be zero, hence zero acceleration.

d. False.
When velocities are negative, positive acceleration is seen in slowing down of body.

Hope that was helpful...

Answer 2

A) True  

Reason :  

When a body is projected upwards its speed at maximum height is zero  but has acceleration downwards which is equal to acceleration due to gravity (g) .

b) False

reason :

Velocity is defined as speed of an object with direction. When speed is zero then magnitude of velocity will zero.

C)True :

Reason :

If An object moves with Constant speed  in straight line then its velocity is constant with time [ remains same]. So acceleration is zero because acceleration is defined as rate of change of velocity .

d)  False

Reason :

Given statement will be true if a and u both are positive.