A cannonball is shot straight up at an initial speed of 98 m/s . The unit vector
ID: 1427659 • Letter: A
Question
A cannonball is shot straight up at an initial speed of 98 m/s . The unit vector j^ is directed upward.
A)What is the speed of the cannonball at 4.0 s ?
b) What is the velocity of the cannonball at 4.0 s ?
C)
What is the speed of the cannonball at 10 s ?
d)
What is the velocity of the cannonball at 10 s ?
e)
What is the speed of the cannonball at 16 s ?
f)
What is the velocity of the cannonball at 16 s ?
g)
What is the speed of the cannonball at 20 s ?
h)
What is the velocity of the cannonball at 20 s ?
Explanation / Answer
along vertical
initial velocity voy = 98 j
acceleration ay = -9.8 j
from equation of motion
vy = voy + ay*t
vy = 98j - (9.8*4)j
vy = 58.8 j m/s
a)
speed = 58.8 m/s
b) velocity = 58.8 j m/s
c)
at t = 10 s
vy = 98j - (9.8*10)j
vy = 0 j m/s
speed = 0
(d)
velocity = 0
(e)
at time t = 16 s
vy = 98j - (9.8*16)j
vy = -58.8 j m/s
speed = 58.8 m/s
(f)
direction = -58.8 j m/s
g)
at time t = 120 s
vy = 98j - (9.8*20)j
vy = -98 j m/s
speed = 98 m/s
h)
velocity = 98 j m/s
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