Kinematics Question 415

Question: From a pole of height 10 m, a stone is thrown vertically upwards with a speed 5 m/s. The time taken by the stone, to hit the ground, it’s n times that taken by it to reach the highest point of it’s path. The value of n is [takeg=10m/s2]

Options:

A) 2

B) 3

C) 4

D) 5

Show Answer

Answer:

Correct Answer: C

Solution:

Given, H=10m , u=5m/s,g=10m/s2

Speed on reaching ground v=u2+2gh Now, v = u + at Now, v=u2+2gh=u+gt

Time taken to reach highest point is t=ug ,

t=u+u2+2gHg=nug(from question)

2gH=n(n2)u2

m(n1)=2gHu2=2×10+105×5=8n=4



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