Dynamics Homework: Find Velocity/Acceleration & Time of Ball Hitting Ground

[ihavaquestion]

Homework Statement

he position of a ball as its kicked upwards is measured as
y(t) =(-4.9 t^2 + 20t + 0.50)m,
where t is measured in seconds. Find the vertical component of velocity and acceleration of the ball as a function of time. If the ground is located at yg = 0, find the time at which the ball hits the ground.

Homework Equations

Cant I take the first and second derivative to find velocity and acc.? then i don't know how to solve for time

The Attempt at a Solution

would velocity= -9.8t + 20
acc.=-9.8??

 

[cepheid]

Cant I take the first and second derivative to find velocity and acc.?

Yes

The Attempt at a Solution

would velocity= -9.8t + 20
acc.=-9.8??

Yes and yes.

then i don't know how to solve for time

Using the expression for y(t), find the t at which y = y_g.