Motion in a Straight Line Questions and Answers Part-8

1. If a body starts from rest and travels 120 cm in the 6th second, then what is the acceleration
a) \[0.20 m\diagup s^{2}\]
b) \[0.027 m\diagup s^{2}\]
c) \[0.218 m\diagup s^{2}\]
d) \[0.03 m\diagup s^{2}\]

Answer: c

2. If a car at rest accelerates uniformly to a speed of 144 km/h in 20 s. Then it covers a distance of
a) 20 m
b) 400 m
c) 1440 m
d) 2880 m

Answer: b

3. The position x of a particle varies with time t as \[x=at^{2}-bt^{3}\]  . The acceleration of the particle will be zero at time t equal to
a) \[\frac{a}{b}\]
b) \[\frac{2a}{3b}\]
c) \[\frac{a}{3b}\]
d) Zero

Answer: c

4. A truck and a car are moving with equal velocity.On applying the brakes both will stop after certain distance, then
a) Truck will cover less distance before rest
b) Car will cover less distance before rest
c) Both will cover equal distance
d) None

Answer: b

5. If a train travelling at 72 kmph is to be brought to rest in a distance of 200 metres, then its retardation should be
a) \[20 ms^{-2}\]
b) \[10 ms^{-2}\]
c) \[2 ms^{-2}\]
d) \[1 ms^{-2}\]

Answer: d

6. The displacement of a particle starting from rest (at t=0) is given by \[S=6t^{2}-t^{3}\]  . The time in seconds at which the particle will attain zero velocity again, is
a) 2
b) 4
c) 6
d) 8

Answer: b

7. What is the relation between displacement, time and acceleration in case of a body having uniform acceleration
a) \[S=ut+\frac{1}{2}ft^{2}\]
b) \[S=\left(u+f\right)t\]
c) \[S=v^{2}-2fs\]
d) none of these

Answer: a
Explanation: \[S=ut+\frac{1}{2}ft^{2}\]

8. Two cars A and B at rest at same point initially. If A starts with uniform velocity of 40 m/sec and B starts in the same direction with constant acceleration of \[4 m\diagup s^{2}\] , then B will catch A after how much time
a) 10 sec
b) 20 sec
c) 30 sec
d) 35 sec

Answer: b

9. A body travels for 15 sec starting from rest with constant acceleration. If it travels distances S1, S2 and S3 in the first five seconds, second five seconds and next five seconds respectively the relation between S1, S2 and S3 is
a) \[S_{1}=S_{2} = S_{3}\]
b) \[5S_{1}=3S_{2} = S_{3}\]
c) \[S_{1}=\frac{1}{3}S_{2} =\frac{1}{5} S_{3}\]
d) \[S_{1}=\frac{1}{5}S_{2} =\frac{1}{3} S_{3}\]

Answer: c
Explanation: If the body starts from rest and moves with constant acceleration then the ratio of distances in consecutive equal time interval S1 : S2 : S3 = 1 : 3 : 5

10. A body is moving according to the equation \[x=at +bt^{2}-ct^{3}\]   where \[x=\] displacement and a,b and c are constants. The acceleration of the body is
a) \[a+2bt\]
b) \[2b+6ct\]
c) \[2b-6ct\]
d) \[3b-6ct^{2}\]

Answer: c