10. (a) A train accelerated from 20 km/hr to 80km/hr in 4 minutes. How much distance does it cover in this period? Assume that the tracks are straight.
(b) A train is travelling with a velocity of 45km/hr. Calculate the distance travelled by it in 1hr, 1 min, 1 sec.
Answers
Answer:
A)
Given :-
Time = 4 minutes = 4/60 hours = 1/15 hours.
Intital Velocity(u) = 20 km/hr
Final Velocity (v) = 80km/hr
for finding Acceleration (a) :-
Use first equation of motion,
v = u + at
⇒ a=v-u/t
⇒a = 80-20/1/15
⇒a = 60 × 15
⇒a = 900km/hr ²
For finding (s) distance :-
Use second equation of motion
s=ut+at²/2
⇒s =20(1/15)+900(1/15)(1/15)/2
⇒s =4/3+2
⇒s =10/3km
Therefore, The distance it covers in this period is 10/3 km
B)
First case :-
Speed = 45 km/hr
Time = 1 hr
Distance = speed x time
= 45 x 1
= 45 km ( 45000 m)
Therefore, the train travels 45 km in 1 hour.
Second case :-
Speed = 45 km/hr or we can also take as
45000 m/ 60 min
Time = 1 min
Distance = speed x time
=( 45000/60 ) x 1
= 45000 / 60
= 750 metres
Therefore, the train travels 750 m in 1 minute.
Third case :-
Speed = 45000 m/ 60 min (or )
45000 m/ 3600sec
Time = 1 second
Distance = speed x time
= (45000 / 3600) x 1
= 45000 / 3600
= 12.5 metres
Therefore, the train travels 12.5 m in 1 second.