Question

1. When will you say a body is in (i) uniform acceleration? (ii) non-uniform acceleration? 2. A bus decreases its speed from 80 km h�1 to 60 km h−1 in 5 s. Find the acceleration of the bus.

Answer 1

Answer:

1》(i) When the velocity of a body changes linearly with time ie,the change in velocity in given period of time at any instant is constant then we will say it is experiencing uniform acceleration.

(ii) When change in velocity in a given period of time varies at every instant then we will say that it is experiencing non-uniform accelaration.

2》u=80km/h=80×5/18m/s=400/18m/s

v=60km/h=60×5/18m/s=300/18m/s

t=5s

Since v=u+at

Therefore a=(v-u)/t

a=(300-400)/(18×5)

a=(-100)/90

Hence acceleration is -1.11m/s^2

Answer 2

$\Large{\underline{\underline{\bf{Solution :}}}}$

★ Uniform Acceleration : When a object is moving with same speed and with same interval of time it is known as uniform Acceleration. For example : A car is moving with 75 km/h. After 1 hour it's speed is same.

$\rule{200}{2}$

★ Non - Uniform Acceleration : When a object is moving with same speed but with different same interval of time it is known as Non - uniform Acceleration. For example : A car is moving with 75 km/h. After 1 hour it's speed is different.

$\rule{200}{2}$

We know that,

$\Large{\implies{\boxed{\boxed{\sf{a = \frac{v - u}{t}}}}}}$

Where,

• a is acceleration
• v is inital velocity = 60 km/h = 16.67 m/s
• u is final velcoity = 80 km/h = 22.2 m/s
• t is time taken = 5 s

______________[Put Values]

$\sf{→ a = \frac{16.67 -22.2)}{5}} \\ \\ \sf{→a = \frac{-\cancel{5.55}}{\cancel{5}}} \\ \\ \sf{→a = -1.11 \: ms^{-2}} \\ \\ \Large{\implies{\boxed{\boxed{\sf{a = -1.11 \: ms^{-2}}}}}}$