September 30
1) Problem 15 on page 73 of your book.
Answer: t = 2 s, d = 60 m
2) David Ortiz hits a homerun, hitting the ball with a velocity of 45 m/s at 40 degrees. What is the
peak height of ball and how far from the plate does it land? Assume that the ball comes back to the
same height that it is hit.
Answer: dy = 41.8 m, dx = 199.4 m
3) George shoots a three-pointer from the top of the key (19 ft 9 in from the hoop) in a basketball game.
George releases his shot 6 ft 4 in above the ground and the hoop is 10 ft tall. If the flight time of
the ball is 1.2 s and the ball reaches its peak 3/4 of the way to the basket, what is the inital
velocity of the ball?
Answer: 10.3 m/s at 60.8 degrees (Hint: There is a lot of extraneous information in this problem.)
4) A silver dollar is thrown downward at an angle of 60 degrees below the horizontal from a bridge 50.0 m
above a river. If its initial speed is 40.0 m/s, where and at what speed will it strike the water?
Ignore the effects of air friction.
Answer: v = 51 m/s, dx = 24.6 m
September 29
1) Julie punts a soccer ball straight up in the air at 13 m/s. If the ball is 1.3 m above the ground
when it is kicked, how high does the ball get? How long is the ball in the air if it comes down and
hits the ground.
2) Baxter (the dog) gets kicked horizontally off a bridge that is 30 m tall at a rate of 6 m/s. How
long does it take for Baxter to hit the water below?
3) If a golf ball is hit at 35 m/s at an angle of 15 degrees, what is the range of the ball (how far
does it go?) in yards?
September 24
Finish the projectile problem that we started in class.
September 23
You are standing on the top of a cliff with your friend and each of you has an indentical rock. Your
friend decides to throw her rock horizontally at 10 m/s. At the same moment, you drop your rock.
Which rock hits the water below first? Explain your answer.
September 19
Study for the test tomorrow. The first lab is also due tomorrow.
September 18
A ball is hurled straight up at 15 m/s, leaving the hand of the thrower 2 m above the ground. Compute
the times and the ball's velocities when it passes an observer at a window in line with the throw,
10 m above the release point.
September 17
A VW Rabbit can go from rest to 80.5 km/hr in 8.2 s. How long will it take to speed up from 48.3 km/hr
to 64.4 km/hr, if the average acceleration is the same as before.
September 16
You decide to launch a ball vertically so that a friend located 20 m above you can catch it. What is
the minimum launch speed you can use? How long after the ball is launched will your friend catch it?
September 11
An osprey accidentally drops a fish, which falls for 3 seconds before hitting the water below. How
high above the water was the osprey when it dropped the fish? How fast is the fish traveling when it
hits the water?
September 10
Add the following vectors together: d1 = 30 km West, d2 = 70 km North.
September 9
A large clock has a second hand that is 1 meter long. Assuming that the hand sweeps smoothly around,
find the velocity of the tip of the hand at exactly 15 seconds after noon.
September 5
How long does it take the sound of thunder to go 1.000 mile traveling at an average speed of 3.314 x 10^2 m/s?
Would it take light more or less time to travel the same distance?