p.99 #1
A baseball rolls off of a .70 m desk and lands
0.25m away? How fast was the ball rolling
(vx)?
ball will freefall in the y dimension until it hits
the ground. So, first you need to find when it
will hit the ground!
0.70
m
0.25 m
p.99 #1
A baseball rolls off of a .70 m desk and lands
0.25m away? How fast was the ball rolling
(vx)?
So we need an
What you know:
equation using
dx = 0.25 m
these variables that
dy = .70 m
g = -9.8 m/s2
tells time to fall .70
vyi=0m/s
m and go 0.25m
1
2
Δy = v yit + gt
2
dy = 4.9t
2
p.99 #1
A baseball rolls off of a .70 m desk and lands
0.25m away? How fast was the ball rolling
(vx)?
Δy = v i t + 0.5gt 2
−.70m = 0t + 0.5(−9.8m / s 2 ) t 2
−.70 = −4.9t 2
.1428 = t 2
t = .378s
€
dx
vx =
t
0.25
vx =
.378s
v x = 0.66m / s
p.99 #2
Cat slides off 1.0m high table and lands
2.2m away. Calculate its speed.
Same problem as #1 essentially
What you know:
dx = 2.2 m
dy = 1 m
g = -9.8 m/s2
vyi=0m/s
p.99 #2
Cat slides off 1.0m high table and lands
2.2m away. Calculate its speed.
Same problem as #1 essentially
−1.0m = 4.9t 2
t = 0.45s
now
2.2
vx =
0.45
v x = 4.9m / s
p.99 #3
A pelican flying along a horizontal path drops a fish
from a height of 5.4m. The fish travels 8.0 m
horizontally before it hits the water below. What is
the pelican’s speed
2
Δy = 5.4 m
Δx = 8 m
vyi =0 m/s
t=?
g =-9.8m/s2
−5.4m = −4.9t
t = 1.05s
now
8
vx =
1.05
v x = 7.6m /s
p.99 #3
If same pelican flying along a horizontal path drops a
fish from a height of 2.7m. The fish travels….
Δy = 2.7 m
Δx = ?
vyi =0 m/s
t=?
g =-9.8m/s2
vx=7.6m/s
−2.7m = −4.9t 2
t = 0.74s
dx
now v x = ....so dx = v x t
t
dx = 7.6m /s(0.74s)
dx = 5.6m