Physics question kinematics

[formal wolf]

Stuck on #2 i tried using the kinematics formula v=v(i)+a(t) to solve for time and i got 24 secs but my teacher got 18 secs

[steep halo]

u need to differentiate x(t)

[steep halo]

you'll then get an euation for v(t)

[formal wolf]

By differentiate you mean make it dx/dt?

[spring shoal]

Hello

Given $x=100-16t^2$

[teal nimbus]

diaas_(yt)

[spring shoal]

First think of how you can find velocity

that will be dx/dt

$\frac{dx}{dt} = v= -32t$

[teal nimbus]

diaas_(yt)

[spring shoal]

After this I want you think of it yourself

[formal wolf]

Since it says v= 0 then we would set it as 0=-32t and then solve for time and get t=0

Then plug t=0 into the function for distance? So it’d be 100m - 16m/s^2(0) and you’d be left with 100 meters?

[steep halo]

yes yes

[steep halo]

since speed is distance/time
dv = dx/dt

after differentiating, you'll get a 1 degree equation for t

like v = the equation

then since you already know v, find t

you'll get the answer as 18

[formal wolf]

Wouldn’t t be 0?

Bc in the equation v=-32(t) when we solve for t we get 0

[steep halo]

im talking about the 2nd one since that's the one you originally asked for