Advertisements
Advertisements
Question
When brakes are applied to a bus, retardation produced is 25 cm s-2 and the bus takes 20 s to stop. Calculate -
- The initial velocity of the bus
- The distance travelled by bus during this time.
Advertisements
Solution
Final velocity (v) = 0
retardation = -25 cm/s2
Expressing it in m s-2
25 cm s-2 = `25/100` m s-2
Hence, - a = - 0.25 m s-2
Time taken (t)= 20 s
(i) Let 'u' be the initial velocity.
Using the first equation of motion,
v = u + at
We get,
u = v - at
u = 0 - (- 0.25)(20)
u = 5 m s-1
(ii) Let 's' be the distance travelled.
Using the third equation of motion,
v2 - u2 = 2as
We get,
∴ (0) 2 - (5)2 = 2 (-0.25) (s)
∴ 0 - 25 = - 0.5 × s
∴ - 25 = - 0.5 s
∴ `(- 25)/(- 0.5)` = s
∴ s = 50 m.
APPEARS IN
RELATED QUESTIONS
A car travels a distance 100 m with constant acceleration and average velocity of 20 ms-1. The final velocity acquired by the car is 25 ms-1.
Find
(i) The initial velocity.
(ii) Acceleration of the car.
How can you find the following?
Displacement from velocity – time graph.
Show the difference between distance and displacement with the help of a diagram.
A body is moving along a circular path of radius r. What will be the distance and displacement of the body when it completes:
Half a revolution
A particle moves along a circular path. How many times does it change its direction in two complete rounds?
A body moves along a circular path of radius r. When it completes three complete rounds, what is the ratio of distance covered to its displacement?
The table below shows the distance travelled by two vehicles A and B during each second:
| Time (s) | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
| Distance travelled by A (m) | 0 | 20 | 80 | 180 | 240 | 300 | 360 | 420 |
| Distance travelled by B (m) | 0 | 10 | 40 | 90 | 160 | 250 | 360 | 490 |
Give the value of the velocity at which they are meeting
Slope of a velocity-time graph gives
An object is dropped from rest at a height of 150 m and simultaneously another object is dropped from rest at a height of 100 m. What is the difference in their heights after 2s if both the objects drop with the same accelerations? How does the difference in heights vary with time?
Distance travelled by a freely falling body is proportional to ______.
