Question

A stone is thrown vertically upward, it reaches a maximum height of 5cm.Calculate-
i) initial speed of stone.
ii) time taken by it to reach the maximum height​

Answer 1

We have,

• The max height of the stone on throwing it that is, 5 cm, in metre, 0.05 m

that's it, fine lets work upon it.

As, we can throwing it upwards, we can say that we can working against gravity and thus the accleration it will go through is nothing but the acceleration due to gravity;

• Acceleration of stone(a) = 10 m/s [Will take it as -10 m/s-² as its is against gravity]

Also, when we will throw the stone, at a point it will be stationary and its final velocity will be 0.

• Final velocity(v) = 0 m/s

Now,

i) initial speed of stone

Using the third equation of motion;

• v² - u² = 2as
• (0)² - u² = 2(-10)(0.05)
• -u² = -1
• u =√ 1
• u = 1 m/s

ii) time taken by it to reach the maximum height

Using first equation of motion;

• v = u + at
• 0 = 1 + (-10)t
• -1/-10 = t
• 0.1 sec = t

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