Question

A stone is thrown horizontally with a speed 1 30 ms− , from the top of a tower of height
180 m. Ignoring air resistance, the acceleration on the stone is only in the vertically
downward direction and is equal to g 10 ms 2 = − . The horizontal part of its motion is a
uniform motion and the vertical part is uniformly accelerated.
(i) The resultant acceleration on the stone during its flight is
(a) 10 ms− (b) 10 root2 ms− (c) 0 (d) 10 root10 ms−
(ii) The time taken by the stone to reach the ground is
(a) 6 s (b) 3 s (c) 4.5 s (d) 9 s
(iii) The distance from the foot of the tower, on the ground, where the stone reaches
the ground is
(a) 180 m (b) 90 m (c) 135 m (d) 270 m
(iv) The speed with which the stone reaches the ground is
(a) 60 ms− (b) 30 root2 ms− (c) 30 root3 ms− (d) 30 root5 ms−

Answer 1

Answer:

Given :     u=30  m/s         θ=45o 

Maximum height reached     H=2gu2sin2θ               (sin245o=0.5)

∴    H=2×10302×0.5=22.5 m