# physics

posted by .

(a) if a train travelling at 72km/hr is to be brought to rest in a distance of 200m then wat should be its retardation
(b) if a body starts from rest and and travels 120 m in 8th sec then wats its acceleration.

• physics -

(a) How do you define retardation?
Is it deceleration?
72 km/h = 20 m/s
Average velocity during deceleration = 10 m/s.
10*t = 200 m
Deceleration time t = 20 s
Deceleration rate = 20 m/s/20s
= 1 m/s^2

(b) If you are supposed to assume the acceleration rate is constant,
X(8) - X(7) = (a/2)*(64-49)
= 120
15*(a/2) = 120
a = 16 m/s^2

• physics -

A motor car moving with a velocity of 54km/hr is brought to rest in (i) 5sec (ii) 3meter. Find the retardation in each case.

• physics -

10*t = 200 m

this is wrong ????? because velocity is 20m/s

## Similar Questions

1. ### physics

a train starts from rest and accelerates uniformly to achieve a velocity of 20m/sec in 10 sec.then train maintains this speed for next 200 sec.the breaks are then applied and train comes to rest in next 50 sec.calculate a)acceleration …
2. ### physics

a train starts from rest and accelerates uniformly to achieve a velocity of 20m/sec in 10 sec.then train maintains this speed for next 200 sec.the breaks are then applied and train comes to rest in next 50 sec.calculate a)acceleration …
3. ### physics

a train starts from rest and accelerates uniformly to achieve a velocity of 20m/sec in 10 sec.then train maintains this speed for next 200 sec.the breaks are then applied and train comes to rest in next 50 sec.calculate a)acceleration …
4. ### physics

if a train at 72kmphr is to be brought to rest in a distance of 200 m then its retardation is A 20m/s^2 b 10m/s^2 c 2m/s^2 d 1m/s^2
5. ### Physics

A car start from rest, moves with uniform acceleration and attains a velocity of 72km/h in 1.5 s it moves with uniform speed for 20 s and is then brought to rest in 10 s under uniform retardation, then total distance travelled using …
6. ### physics

a macopolo of a mass 1200000g travelling at 72km/h is brought to rest in 4s.with the aid of a diagram,find its (a)average retardation (b)average breaking distance (c)the total distance moved during deceleration
7. ### Physics

An electric train leaves a station starting from rest and attains a speed of 72km/hr in 10 second. It travels at that speed for 120 seconds. Then it undergoes uniform retardation for 20 seconds to come to halt at the next station calculate …
8. ### physics

A body moving with a velocity of 3m/s is brought to rest by a constant force after travelling 15m, calculate the retardation.
9. ### Physics

An electric train leaves a station starting from rest and attains a speed of 72km/hr in 10 second. Then it undergoes uniform retardation for 20 second to come to halt at the next station then calculate i) the distance between the train …
10. ### physics

a particle starts from rest and travels a distance x with uniform acceleration, then it travels a distance 2x with uniform speed ,finally it travels a distance of 3x with uniform retardation and comes to rest. If the whole motion of …

More Similar Questions