48 Science -- Force

A stone is thrown upwards with a velocity of 72 km/hr. If the air resistance is neglected, find the maximum height travelled by it and the time taken for it to return the initial position?

1 Answers

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Given

initial velocity ( u ) = 72 km/hr = 72 x 1000 / 3600

= 20 m/s

acceleration due to gravity (g) = 10 m/s²

also, final velocity(v) = 0 m/s

for maximum height,

v² = u²- 2gH

or, 0 = 20² - 2 x 20 H

thus, H = 400/ 40

maximum height (H) = 10 m

again , for time to return to initial position.

total displacement(s) = 0

so,

s= ut - 1/2 gt²

or, ut = gt²

thus, T = u/g

= 20/10

total time taken = 2 sec

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Solution:

Initial velocity of car (u) = 45 km/hr = 45 * 1000/3600 = 12.5 m/s

Time taken (t) = 3 s

Since the car stops finally, final velocity of car (v) = 0 m/s

Now,

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