Transcript Chapter 6 Motion in Two Directions

Chapter 6
Motion in Two Directions
Projectile Motion
Projectile- object shot through the air
Trajectory- the path that a projectile follows
How can horizontal and vertical displacement be
determined?
1. Vertical displacement
dy= ½gt2 + vit
if vi=0 then dy= ½gt2
2. Horizontal displacement
dx= vxt
Example
•
A stone is thrown horizontally at 15m/s. It
is thrown from the top of a cliff 44 m high.
a. How long does it take the stone to reach
the bottom of the cliff?
b. How far from the base of the cliff does the
stone strike the ground?
Example
A projectile is launched horizontally from the
top of a building with a velocity of 12.7m/s.
At what height is the projectile launched if
the projectile lands 15.0 m from the side of
the building?
Projectiles Launched at an Angle
• A golf ball is hit and leaves the tee with a
velocity of 25.0 m/s at 35.0° with respect to
the horizontal. What is the horizontal
displacement of the ball?
V= 25.0 m/s
= 35.0°
d x= ?
t=?
Example
•
A projectile is fired with a velocity of 19.6 m/s
at an angle of 60.0° with the horizontal.
a. Calculate the vertical and horizontal velocity of
the projectile.
b. Calculate the time the projectile is in the air.
c. Determine the horizontal displacement that the
projectile travels.
d. Determine the maximum height the projectile
reaches.
Circular Motion
• Centripetal acceleration
• - center-seeking acceleration of an object
moving in a circle.
How is it determined?
Ac= v2/r or
Ac= 42r/T2
Centripetal Force
• Net force directed toward the center of a circle
How is it determined?
Fnet= mac
Example: A 13g rubber stopper is attached to a 0.93
m string. The stopper is swung in a horizontal
circle, making one revolution in 1.18s. Find the
tension force exerted by the string on the stopper.
Relative Velocity
•
•
Motion is relative to an observer
Example: A motor boat traveling 6.0 m/s, East
encounters a current traveling 3.8 m/s, South.
a. What is the resultant velocity?
b. If the width of the river is 120 m wide, then how
much time does it take the boat to travel shore to
shore?
c. What distance downstream does the boat reach
the opposite shore?