00:01
To find the velocity and the acceleration, in question a, we want to find the velocity and acceleration, so we need to take our first derivative of s and our second derivative of s.
00:11
For velocity, we get 24 minus 1 .6t, and for acceleration, we get 1 .6.
00:18
For b, we want to find how long does it take the rock to reach its highest point? so at the highest point, velocity is zero, so we can use this equation.
00:26
0 is equal to 24 minus 1 .6t, and we get t is 15 seconds.
00:33
For part c, we want to see how high does a rock go.
00:36
So at 15 seconds, we plug this into our kinematics expression.
00:41
S is equal to 24 times 15 minus 0 .8 times 15 squared, and we get 180 meters.
00:48
D asks how long does it take the rock to reach half its maximum height? so at half of 180, we get 90.
00:55
90 is equal to 24t minus 1 .5...