Q. 64.5( 2 Votes )
A car A is travelling on a straight level road with a uniform speed of 60 km/h. It is followed by another car B. Which is moving with a speed of 70 km/h. When the distance between them is 2.5 km, the car B is given a deceleration of 20 km/h2. After how much time will B catch up with A?
A. 1 h
Distance covered by car A in time t is, s1 = 60 t
For car B:
Using the second equation of motion: s = ut + at2
where: s = distance covered = s2
u = initial velocity = 70 km/h
a = acceleration = -20 km/h
t = time = t
s = ut + at2
s2 = 70t + (-20) × t2
s2 = 70t – 10 t2
But it is given that s2 – s1 =2.5 km
70t – 10 t2 - 60 t = 2.5
10t - 10 t2 = 2.5
t – t2 = 0.25
t – t2 – 0.25 =0
t2 –t +0.25 =0
(t – 0.5)2 =0
t = 0.5 hr
Rate this question :
A cheetah starts from rest, and accelerates at 2 m/s2 for 10 seconds. Calculate :
(a) the final velocity
(b) the distance travelled.Lakhmir Singh & Manjit Kaur - Physics
Obtain a relation for the distance travelled by an object moving with a uniform acceleration in the interval between 4th and 5th second.All In One - Science
A car accelerates from 6 ms–1 to 16 ms–1 in 10 sec. Calculate (a) the acceleration and (b) the distance covered by the car in that time.Together with Science
A bus increases its speed from 36 km/h to 72 km/h in 10 seconds. Its acceleration is :Lakhmir Singh & Manjit Kaur - Physics
Starting from rest at the top of an inclined plane a body reaches the bottom of the inclined plane in 4 second. In what time does the body cover one-fourth the distance starting from rest at the top?Evergreen - Science
A bus is moving with a speed 72 km/h can be stopped by brakes after at least 10 m. What will be the minimum stopping distance, if the same bus is moving at a speed of 144 km/h?All In One - Science
Derive the formula: ,where the symbols have usual meanings.Lakhmir Singh & Manjit Kaur - Physics
The speed-time graph of an ascending passenger lift is given alongside.
What is the acceleration of the lift :
(i) During the first two seconds?
(ii) between second and tenth second?
(iii) during the last two seconds?Lakhmir Singh & Manjit Kaur - Physics
A car is moving on a straight road with uniform acceleration. The speed of the car varies with time as follows :
Draw the speed-time graph by chooding a convenient scale. From this graph :
(i) Calculate the acceleration of the car.
(ii) Calculate the distance travelled by the car in 10 seconds.Lakhmir Singh & Manjit Kaur - Physics