1. Find the average velocity over the time interval [0,3] if the displacement is given by s(t)=t3-2.0t2+1.2t+5. Round your answer to two decimal places.
2. A ball is thrown vertically upward from ground level. Its height, in feet, at time t, in seconds is given by s(t)= -16t2+80.0t. What is the initial velocity of the ball in feet per second? Round your answer to two decimal places and omit the units of measurement.
3. A ball is thrown vertically upward from ground level. Its height, in feet, at time t, in seconds is given by s(t)= -16t2+60.0t+60. What is the initial velocity of the ball in feet per second? Round your answer to two decimal places and omit the units of measurement.
4. A particle moves in a straight line in such a way that the position in time is given by s(t)=t3-5.3t2+2.3t+1.Starting from time t=0, when is the first time that the particle starts moving in the negative direction? Round your answer to two decimal places.