The distance, d, through which a stone falls from rest varies directly as the square of the time, t, taken. If the stone falls 45cm in 3 seconds, how far will it fall in 6 seconds?
- 90cm
- 135cm
-
180cm
- 225cm
The correct answer is: C
Explanation
d \(\alpha\) t2d = t2 k
where k is a constant. d = 45cm, when t = 3s; thus 45 = 32 x t
k = \(\frac{45}{9}\) = 5
thus equation connecting d and t is d = 5t2
when t = 6s, d = 5 x 62
= 5 x 36
= 180cm