CP Physics
Two Dimensional Motion and Vectors HW #3
1) Define projectile motion.
Name _______________________
2) In the absence of air resistance, why does the horizontal component of velocity for a projectile remain constant
while the vertical component changes?
3) How does the downward component of the motion of a projectile compare with the motion of free fall?
4) At the instant a ball is thrown horizontally over a level range, a ball held at the side of the first is released and
drops to the ground. If air resistance is neglected, which ball strikes the ground first? Explain your answer.
5) A projectile is launched vertically at 100 m/s. If air resistance can be neglected, at what speed will it return to at
its initial level?
6) Suppose you drop an object from an airplane traveling at a constant velocity and air resistance doesn’t affect the
falling object. Draw its falling path as observed by someone at rest on the ground, not directly below but off to
one side.
What would be the falling path as observed by you looking downward from the airplane ignoring air resistance?
Where would the object strike the ground relative to you in the airplane ignoring air resistance?
Where would it strike if air resistance affects the fall?
CP Physics
Two Dimensional Motion and Vectors HW #3
Name _______________________
7) A projectile is fired straight upward at 141 m/s. How fast is it moving upward at the instant it reaches the top of
its trajectory?
Suppose instead it were fired upward at a 45o angle. What would the y component of its velocity be the top of
its trajectory?
For all of these problems ignore the effects of air resistance. Draw a picture to help you visualize the problem. Show all
your work and the correct units for full credit.
8) A ball is projected horizontally off of the top of a cliff with a speed of 15 m/s. If the cliff is vertical and its height
is 56 m, how long does it take the ball to hit the ground?
9) In the above problem, what horizontal distance from the base of the cliff does the ball land?
10) One crazy physics teacher was standing on top of tall building and wondered what the height of the building
was. The teacher threw a physics book (that was all she ever carried) horizontally off the building at 4.0 m/s. The
teacher found the book, open to chapter 3. The book was 16 meters from the base of the building. How long did
it take the book to fall?
11) What is the height of the tall building?
CP Physics
Name _______________________
Two Dimensional Motion and Vectors HW #3
12) Have you ever watched movie where people fall into a pool below their balcony? How long would it take to
jump into the pool if it is 15 meters out from the bottom of their balcony that is 75 meters high?
13) For the above problem, how fast would a person have to jump horizontally to reach the pool instead of the
pavement?
14) How high is a cliff if it takes 6 seconds for a rock to hit the ground below after the rock is thrown horizontally off
the cliff?
15) Why doesn’t it matter how fast you throw the rock?