Question

17. A car traveling at 36km/hr speeds upto 70km/hr in 5 seconds. What is its acceleration?
the same car stops in 20s, what is the retardation?
16. A scooter acquires a velocity of 36km/hr in 10seconds just after the start. It takes 20
seconds to stop. Calculate the acceleration in the two cases.
19. On a 120km track, a train travels the first 30 km at a uniform speed of 30 km/hr. How fa
must the train travel the next 90 km so as to average 60 km/hr for the entire trip?
20. A train travels at 60 km/hr for 0.52 h at 30 km/hr for the next 0.24 hr and at 70 km/hr fd
the next 0.71 hr. What is the average speed of the train?​

Answer 1

Answer:

17. Answer......

1.7 m/s^2

Explanation:

Answer 2

Hello friend

first case ( when the car accelerates )

GIVEN

Initial velocity (u)  = 36km/hr = 36 x 5/18 = 10 m/s

Final velocity (v) = 70 km/hr = 70 x 5/18 = 19.4 m/s

Time  (t)  = 5 sec

WE KNOW THAT   a = v-u/t  

so a = ( 19.4 - 10 ) / 5  

a= 9.4/5

a= 1.88 m/s²

Second case ( when car retards )  

GIVEN

Initial velocity (u)  = 36km/hr = 36 x 5/18 = 10 m/s

Final velocity (v) = 0 (AS CAR STOPS)

Time  (t)  = 20 sec

Using first equation of motion, we get  

v = u + at

0 = 20 + 20a

- 10 = 20a  

-0.5 m/s²  

So the retardation of car is -1m/s²

Explanation:

HOPE IT HELPS U......................