Motion in a Straight Line Questions and Answers Part-17

1. A stone is shot straight upward with a speed of 20 m/sec from a tower 200 m high. The speed with which it strikes the ground is approximately
a) 60 m/sec
b) 65 m/sec
c) 70 m/sec
d) 75 m/sec

Answer: b

2. A body freely falling from the rest has a velocity ‘v’ after it falls through a height ‘h’. The distanceit has to fall down for its velocity to become double, is
a) 2h
b) 4h
c) 6h
d) 8h

Answer: b

3. Velocity of a body on reaching the point from which it was projected upwards, is
a) \[v=0\]
b) \[v=2u\]
c) \[v=0.5u\]
d) \[v=u\]

Answer: d
Explanation: Body reaches the point of projection with same velocity

4. A body projected vertically upwards with a velocity u returns to the starting point in 4 seconds. If \[g=10 m\diagup sec^{2}\]   , the value of u is
a) 5 m/sec
b) 10 m/sec
c) 15 m/sec
d) 20 m/sec

Answer: d

5. Time taken by an object falling from rest to cover the height of \[h_{1}\] and \[h_{2}\] is respectively \[t_{1}\] and \[t_{2}\] then the ratio of \[t_{1}\] to \[t_{2}\] is
a) \[h_{1}:h_{2}\]
b) \[\sqrt{h_{1}}:\sqrt{h_{2}}\]
c) \[h_{1}:2h_{2}\]
d) \[2h_{1}:h_{2}\]

Answer: b

6. A body is thrown vertically up from the ground. It reaches a maximum height of 100m in 5 sec. After what time it will reach the ground from the maximum height position
a) 1.2 sec
b) 5 sec
c) 10 sec
d) 25 sec

Answer: b
Explanation: Time of ascent = Time of descent = 5 sec

7. A body thrown vertically upwards with an initial velocity u reaches maximum height in 6 seconds. The ratio of the distances travelled by the body in the first second and the seventh second is
a) \[1:1\]
b) \[11:1\]
c) \[1:2\]
d) \[1:11\]

Answer: b

8. A body, thrown upwards with some velocity, reaches the maximum height of 20m. Another body with double the mass thrown up, with double initial velocity will reach a maximum height of
a) 200 m
b) 16 m
c) 80 m
d) 40 m

Answer: c

9. A balloon starts rising from the ground with an acceleration of \[1.25 m\diagup s^{2}\]   after 8s, a stone is released from the balloon. The stone will\[\left(g=10 m\diagup s^{2}\right)\]
a) Reach the ground in 4 second
b) Begin to move down after being released
c) Have a displacement of 50 m
d) Cover a distance of 40 m in reaching the ground

Answer: a

10. A body is thrown vertically upwards with a velocity u . Find the true statement from the following
a) Both velocity and acceleration are zero at its highest point
b) Velocity is maximum and acceleration is zero at the highest point
c) Velocity is maximum and acceleration is g downwards at its highest point
d) Velocity is zero at the highest point and maximum height reached is \[u^{2} \diagup 2g\]

Answer: d