Question

Question #ccfdd

Answer 1

4 seconds

Explanation:

Using the equation of motion `V = U + a*t` where
V is the final speed
U is the initial speed
a is acceleration
t is time

The body is travels straight up, slowing down due to gravity, until it reaches a speed of `0 ms^-1` (the apogee) and then accelerates back down to earth in the same time

let `gms^-2` be the acceleration due to gravity

Therefore, the time in the initial equation is half the total time, the final speed is 0 and the acceleration is `-gms^-2`
Substituting these values into the equation
`0 = U -gms^-2*1s`
Therefore the initial speed is `gms^-1`

Putting the new value for U (`2gms^-1`) back into the equation we can solve for `t`
`0 = 2gms^-1 - gms^-2*ts`
t = 2 seconds for launch to the apogee, therefore the total time for the second journey is 4 seconds