Question

Question 32:
An aircraft travelling at 600 km/h accelerates steadily at 10 km/h per second. Taking the speed of sound as 1100 km/h at the aircraft’s altitude, how long will it take to reach the ‘sound barrier’ ?

Lakhmir Singh Physics Class 9

Answer 1

The aircraft has to sound barrier , i.e.,

v = 1100 km/h = 1100 × 5 / 18 = 2750 / 9 m/S

u = 600 km/h = 600 × 5 / 18 = 1500 / 9 m/s

The acceleration of the aircraft 10 km/h per second

a = 10 km / h / s = 10 × 5/18 m/s/s = 25/9 m/s²

Using first equation of motion

v = u + at

2750 / 9 = 1500 / 9 + 25t / 9

2750 = 1500 + 25t
27500 -
1500/25 = 1250/25 = 50s

Hence , the aircraft will cross the sound barrier in 50s .

Answer 2

Initial Distance=600km/h
Final Distance=1100km/h
Acceleration=10km/h
Time=x
since we know that,
$acceleration = \frac{final - initial \: positon}{time}$
$10 = \frac{1100 - 600}{x}$
$x = \frac{500}{10} = 50sec$