Chapter 07 Motion Questions-03
Questions
1. When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Show Answer
Answer
(i) A body is said to be in uniform acceleration if it travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time.
(ii) A body is said to be in nonuniform acceleration if the rate of change of its velocity is not constant.
2. A bus decreases its speed from $ \text{80km} h^{-1} $ to $ \text{60km} h^{-1} $ in 5 s. Find the acceleration of the bus.
Show Answer
Answer
Initial speed of the bus, $u=80 km / h=80 \times \frac{5}{18}=22.22 m / s$
Final speed of the bus, $v=60 km / h=60 \times \frac{5}{18}=16.66 m / s$
Time take to decrease the speed, $t=5 s$
Acceleration, $a=\frac{v-u}{t} \quad=\frac{16.66-22.22}{5}=-1.112 m / s^{2}$
3. A train starting from a railway station and moving with uniform acceleration attains a speed 40 km h–1 in 10 minutes. Find its acceleration.
Show Answer
Answer
Initial velocity of the train, $u=0$
Final velocity of the train, $v=40 km / h \quad=40 \times \frac{5}{18}=11.11 m / s$
Time taken, $t=10 min=10 \times 60=600 s$
Acceleration, $a=\frac{v-u}{t}=\frac{11.11-0}{600}=0.0185 m / s^{2}$
Hence, the acceleration of the train is $0.0185 m / s^{2}$.
