If a ball released from a height of 20m, How long would it take the ball to reach the ground? (assures g = 10m/s)
A
2sec
B
3sec
C
35sec
D
2.4sec
Verified Correct Answer: A.
Physical Principles & Numerical Solution
Using the equation
S = ut + ½ gt2
H = s = 20m, t = ?
G =10m/s2, u = 0m/s
20 = 0 × t × ½ × 10 t
20 = 5t
i.e 5t2 = 20
t = 20/5 = 4
t = 4 (squaring both sides)
√ t2 = √4
= 2sec
∴ t = 2sec
Source: Myschool Past Questions Archive (Record #40857)