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/s∙ 2 (4s)∙ 2

d= -5 m/s2 16 s∙ 2 = -3.5 m2.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

3. 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

4. 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) √0.05 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.