Monday 21 Sep:

Target: Use of motion equations  (& Quiz)

Journal:

 1. A ball is shot with a vertical  velocity of 20 m/s from the ground.

a. How long will it take to hit the ground?

b. What height will it reach?

c. What is the velocity when it hits the ground?

a.  V_f = V_o + at  

   -20m/s = 20m/s + (-10m/s²)(t)

   -40m/s / -10m/s^{2 =} t

      t = 4.0s

b. X_y = V_ot + ½ at² 

X_y  =  (20m/s) (2.0s) + (.5)(-10)(2)²

X_y  =  20m

2. A ball is shot to a height of 100m from the ground.

a. What was the initial velocity?

b. How long did it take to reach the apex?

a. V_f² – V_o² = 2aDX

    0 – V_o²  = 2(-10m/s²)(100m)

     V_o =  -(-2000)^-2   --> 44.7m/s

b. V_f = V_o + at  

   0 = 44.7m/s  + (-10m/s²)(t)

      t = 4.47s

Correct Pre-Test