Question

Question 36:
(a) Write the three equations of uniformly accelerated motion. Give the meaning of each symbol which occurs in them.
(b) A car acquires a velocity of 72 km per hour in 10 seconds starting from rest. Find
(i) the acceleration,
(ii) the average velocity, and
(iii) the distance travelled in this time.

Lakhmir Singh Physics Class 9

Answer 1

a) V = u + at

s = ut + 1/2 at²

v² = u² + 2as

v = Final velocity

u = Initial velocity

a = acceleration

s = displacement


b) Initial velocity = u = 0

Final velocity = v = 72 km/hr = 72 × 5/18 = 20m/s

Time = t = 10 sec

i ) Acceleration = a

Equation of motion :-

v = u + at

20 = 0 + 10a

a = 20/10

a = 2m/s²

ii ) Displacement = distance traveled = s

Equation of motion :-

v² - u² = 2as

20² = 2 × 2 × s

400 = 4s

s = 400/4

s = 100 m


iii ) Average velocity = displacement / time

= 100/10

= 10 m/s