Download Ch.2 HW 6

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HW. Ch. 2 #6 Help I’m Falling and I Can’t Keep From Accelerating!
1. Mr. Vining and Aquila are hiking around the Grand Canyon when Mr. Vining kicks a rock and Aquila
chases it off the cliff and falls freely from rest for 8.0 s (a = -10.0 m/s2). How fast would Aquila be moving just
before she reaches the bottom of the canyon?
a. What variables do you know and which are unknown?
b. What equation are you going to use to solve this problem?
c. Solve the equation for the unknown without using numbers (unless they are already in the equation).
d. Calculate her final speed. (-80. m/s)
e. What distance does she fall during this time? (-320 m)
2. A frustrated physics student drops his Physics book from a bridge that is 120. m high. With what speed does
the book hit the ground? You must identify all variables and show the equation to be used before solving for
the problem. (-49.0 m/s)
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3. A weather balloon is floating at a constant height above the earth when it releases a pack of instruments. If
the pack hits the ground with a speed of 73.5 m/s how high is the balloon?
a. What variables do you know and which are unknown?
b. What equation are you going to use to solve this problem?
c. Solve for the height. (270. m)
d. How long does the pack fall? Do not use the distance you found in b. You must identify all variables, show
the equation to be used and solve the equation for the missing variable before solving for the problem. (7.35 s)
4 (37. a) If a freely falling rock were equipped with a speedometer, by how much would its speed readings
increase with each second of fall?
b) Suppose the freely falling rock were dropped near the surface of a planet when g=20 m/s2. By how much
would its speed readings change each second?
5 (38.) If a freely falling rock were equipped with an odometer, would the readings for distance fallen each
second stay the same, increase with time, or decrease with time? Why?
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6 (39) a. When a ball is thrown straight up, by how much does the speed decrease each second neglect air
resistance?
b. After the ball reaches the top and begins its return back down, by how much does its speed increase each
second?
c) Compare the times going up and coming down.
7 (40.) Table 2.2 in the book shows the instantaneous speed of an object dropped from rest is 10 m/s after 1
second of fall. Table 2.3 shows that the object has fallen only 5 meters during this time. Your friend says this is
incorrect, because distance traveled equals speed times time, so the object should fall 10 meters. What do you
say?
8 (41.) A ball is thrown straight up. What will be the instantaneous velocity at the top of its path? What will
be its acceleration at the top? Why are your answers different?
9 (49.) Mr. Vining and Mr. Hill are out shooting hoops one day with Steve Nash when they decide to teach
Steve about the physics of basketball by calculating Steve’s’ hang time. They measured that Steve can jump a
vertical distance of 0.75 meters, so what would his hang time be? Don’t forget the drill.
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10. Mr. Hill and Mr. Vining got tired of shooting hoops and started having a water balloon fight. As things
progressed they moved to a set of stairs when the spotted Mr. Johnson coming their way and decided to drop
water balloons on him. Mr. Hill was 9.0 m above the ground and Mr. Vining was 5.8 m above the ground.
a. If they drop them at exactly the same time whose balloon will hit first?
b. How long will it take for Mr. Vining’s balloon to hit the ground? Don’t forget the drill.
c. How fast will Mr. Vining’s balloon be going when it hits the ground? Don’t forget the drill.
d. How long will it take for Mr. Hill’s balloon to hit the ground? Don’t forget the drill.
e. How fast will Mr. Hill’s balloon be going when it hits the ground? Drill Drill Drill!
f. What is the time difference between the two balloons?
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