Physics
Answer
The difference between uniform velocity and variable velocity is as follows:
| Uniform Velocity | Variable Velocity (or non-uniform) |
|---|---|
| If a body travels equal distances in a particular direction, in equal intervals of time, the body is said to be moving with a uniform velocity. | If a body moves unequal distances in a particular direction in equal intervals of time or it moves equal distances in equal intervals of time, but its direction of motion does not remain the same, then the velocity of the body is said to be variable (non uniform). |
| Example — A body, once started on a frictionless surface, moves with uniform velocity. | Example — The motion of a body in circular path, even with uniform speed is with variable velocity as the direction of motion of body continuously changes with time. |
Related Questions
Assertion (A) : The velocity-time graph of a body in motion can be a straight line parallel to the time axis.
Reason (R) : This is because the motion of body is with non-uniform velocity.
- Both A and R are true and R is the correct explanation of A
- Both A and R are true and R is not the correct explanation of A
- Assertion is false but reason is true
- Assertion is true but reason is false
Assertion (A) : The acceleration-time graph of а body is a straight line parallel to time axis.
Reason (R) : This depicts the motion of freely falling body under gravity.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
Assertion (A) : Acceleration of a moving body is always positive.
Reason (R) : Acceleration is the rate of change of velocity with time.
- both A and R are true and R is the correct explanation of A
- both A and R are true and R is not the correct explanation of A
- assertion is false but reason is true
- assertion is true but reason is false
A lift starts from rest at the ground floor and moves vertically upward along a straight shaft. During the first 4 s, the lift moves with uniform acceleration and attains a velocity of 2 m s-1. It then moves with uniform velocity for the next 6 s. Finally, it is brought to rest uniformly in 2 s at the top floor.
Assuming the motion to be one-dimensional, answer the following:
(a) Calculate the acceleration of the lift during the first 4 s.
(b) Calculate the total height between the ground floor and the top floor.
(c) Draw the velocity-time graph for the complete motion and mark the regions of acceleration, retardation and zero acceleration.
(d) Use the graph to calculate the average velocity of the lift during the upward journey.
(e) If the lift now moves downward following the same pattern, how would the signs of acceleration and displacement change?
(f) "The lift has maximum acceleration when it starts moving." Is this statement correct? Give reason.