Advertisements
Advertisements
Question
A toy car initially moving with uniform velocity of 18 km h-1 comes to a stop in 2 s. Find the retardation of the car in S.I. units.
Advertisements
Solution
initial velocity (u) = 18 km/h-1
final velocity (v) = 0 km/h
time (t) = 2 s
acceleration/retardation (a) = ?
To convert initial velocity u to m s-1
18 km/h-1 = `(18 " km")/(1 " h")`
= `(18 xx 1000 " m")/(60 xx 60 " s")`
⇒ 18 km/h-1 = `(18 xx 10 " m")/(6 xx 6 " s")`
⇒ 18 km/h-1 = 5 m s-1
Acceleration (a) = `("Final Velocity "("v") - "Initial Velocity "("u"))/("time "("t"))`
a = `(0 - 5)/2` m s-2
a = `-(5 "ms"^-1)/"2s"`
a = -2.5 m s-2
Hence, acceleration of the body is -2.5 m s-2. Negative sign shows that the velocity decreases with time, so retardation is 2.5 m s-2.
APPEARS IN
RELATED QUESTIONS
Give a scientific reason.
When an object falls freely to the ground, its acceleration is uniform.
An object of mass 16 kg is moving with an acceleration of 3 m/s2. Calculate the applied force. If the same force is applied to an object of mass 24 kg, how much will be the acceleration?
Figure shows the velocity-time graphs for two cars A and B moving in the same direction. Which car has greater acceleration? Give reasons to your answer.
If a body is moving with a constant velocity its acceleration is ______.
Draw velocity – time graph for the following situation:
When a body is moving with variable velocity, but uniform retardation.
The speed of a car increases from 10 km/h to 64 km/h in 10 seconds. What will be its acceleration?
The graph shows how the velocity of a scooter varies with time in 50 s.
Work out: Deceleration
The speed of a particle is constant. Will it have acceleration? Justify with an example.
An object can be moving with uniform speed but with variable acceleration.
Assertion: A positive acceleration of a body can be associated with the slowing down of the body.
Reason: Acceleration is a vector.
