Calculate the time taken for a mango fruit that fall from the tree 20 m to the ground [g = 10 ms-2]
A
10s
B
5s
C
4s
D
2s
Verified Correct Answer: D.
Physical Principles & Numerical Solution
u = , H = 20, g = 10
From equation of motion under gravity
H = ut ± \(\frac{1}{2}\)gt2, It is falling so g is +ve
H = 0 + \(\frac{1}{2}\)gt2
H = \(\frac{1}{2}\)gt2
2H = gt2
\(\frac{2H}{g}\) = t2
t = \(\frac{\sqrt{2H}}{g}\)
= \(\frac{\sqrt {2 \times 20}}{10}\)
= √4
= 2s
Source: Myschool Past Questions Archive (Record #46464)