An object is thrown upward with a vertical velocity of 128 ft./sec. It will return in

Options

A. 64 seconds
B. 16 seconds
C. 8 seconds
D. 4 seconds

Answer

C

Explanation

S, the distance equals zero when the object has returned . `V_0`, the initial velocity equals 128 ft/sec. g, the acceleration of gravity equals `32 ft//sec^2`
`0=128t-(32t^2)/2=128t-16t^2`
`16t^2-128t=0`
Factoring , t(16t-128)=0
When the product equals zero , one of the factors must equal zero Either t=0 (not valid)
or 16t-128=0 and `t=128/16`=8 sec