Answer:
0.49 seconds, 4.8(02)m/s
Explanation:
a) first convert 120cm to metres
that is 1.2m
suvat says that s = ut + ½ at²
let's rearrange that for time
t = -((u ± √(u² + 2as))/a)
u = 0
a = 9.8
s = 1.2
t = -((0 ± √(0 + 2(9.8)(1.2)))/9.8)
t = -((±√23.52)/9.8)
t = either 0.49 or -0.49 seconds.
since it cannot happen in negative time, the answer is 0.49 seconds
b) a = (v - u) / t
rearrange for v
v = u + at
a = 9.8
t = 0.49
u = 0
v = 0 + 9.8(0.49)
v = 4.8
or to be more specific, 4.802 m/s
