1. A construction worker accidently drops a brick from a high scaffold 1. A construction worker accidently drops a brick from a high scaffold. A) What is the velocity of the brick at the 4 seconds? B) how far does the brick fall during this time? 2. A student drops a ball from a window 3.5 meters above the sidewalk. How fast is it moving when it hits the ground?

1a. v= v + at, so v= 0 + (-10 m/s2 )∙ 4 s v= -40 m/s 1b. d= vt + 1/2at2 , so d= 0 + ½ ∙ -10 m/s2 ∙ (4s)2 d= -5 m/s2 ∙ 16 s2 = -3.5 m d= 1/2at2 so -3.5 m = ½ (-10 m/s2) (t2) -3.5 m = -5 m/s2 (t2) √0.7 s2 = √t2 -5 m/s2 -5 m/s2 0.84 s = t v = v + at so v = -10 m/s2 ∙ 0.84 s = -8.4 m/s

A tennis ball is thrown straight up with an initial speed of 20. 0 m/s A tennis ball is thrown straight up with an initial speed of 20.0 m/s. It is caught at the same distance above the ground. a) How long does the ball remain in the air? b) How high does the ball rise?

Lets start with b first: b) It takes the ball 2 seconds on the way up to run out of speed and then 2 seconds on the way back down for a total of 4 seconds. a) Since it takes 2 seconds on the way up then that is our time for finding distance d = ½ at2 d = 20 m

You decide to flip a coin to determine whether to do your Physics or English homework first. The coin is flipped straight up. a) If the coin reaches a high point of 0.25 m above where you released it, what is its initial speed? b) If it land right back in your hand, how much time did it spend in the air?

4a. d = ½ at2 so 0. 25 m = ½ (-10 m/s2) (t2) 0. 25 m = -5 m/s2 (t2) √0 4a. d = ½ at2 so 0.25 m = ½ (-10 m/s2) (t2) 0.25 m = -5 m/s2 (t2) √0.05 s2 = √t2 -5 m/s2 -5 m/s2 0.22 s = t vf = vi + at; 0 = v + (-10 m/s2 )(0.22s); vi = 2.2 m/s 4b. It takes 0.22 s up and 0.22 seconds down. That totals 0.44 s.