Tutorial Exercise A ball is thrown into the air with a velocity of 46 ft s Its height in feet after t seconds is given by s t 46t 16t2 Find the velocity of the ball at time t 2 seconds Step 1 Let h s t 46t 16t2 give the height of the ball at time t Then the ball s velocity at time t a can be found by s t s a t a v a lim t a We are asked to find the velocity at t 2 therefore we use a v 2 lim s t s 2 t 2 t 2 lim t 2 lim t 2 46t 16t 46 16 2 46t 16t2 t 2 t 2 and have