Advertisements
Advertisements
Question
A stone thrown vertically upwards takes 3 s to attain maximum height. Calculate
- initial velocity of the stone
- maximum height attained by the stone. (Take g = 9.8 ms−2)
Advertisements
Solution
Initial velocity of the stone = u =?
At highest point, final velocity = v = 0
Time = t = 3s
Acceleration = a = −g = −9.8 ms−2
Maximum height attained by stone = S = h = ?
(i) v = u + at
0 = u + (−9.8) 3
u = 9.8 × 3 = 29.4 ms−1
(ii) Now, S = ut + `1/2` at2
h = `(29.4)3+1/2(-9.8)(3)^2` = 88.2 − 4.9 × 9
= 88.2 − 44.1 = 44.1 m
APPEARS IN
RELATED QUESTIONS
Explain why, the motion of a body which is moving with constant speed in a circular path is said to be accelerated.
A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.
Which of the following could not be a unit of acceleration?
When is the negative acceleration?
Multiple choice Question. Select the correct option.
At the maximum height, a body thrown vertically upwards has :
A packet is dropped from a stationary helicopter, hovering at a height ‘h’ from ground level, reaches the ground in 12s. Calculate
- the value of h
- final velocity of packet on reaching the ground. (Take g = 9.8 ms−2)
A girl walks along a straight path to drop a letter in the letterbox and comes back to her initial position. Her displacement–time graph is shown in Fig.8.4. Plot a velocity-time graph for the same.
The velocity-time graph (Fig. 8.5) shows the motion of a cyclist. Find (i) its acceleration (ii) its velocity and (iii) the distance covered by the cyclist in 15 seconds.
Two stones are thrown vertically upwards simultaneously with their initial velocities u1 and u2 respectively. Prove that the heights reached by them would be in the ratio of `"u"_1^2 : "u"_2^2` (Assume upward acceleration is –g and downward acceleration to be +g)
When will you say a body is at uniform acceleration?
