Physics 135: Discussion Set # 4
Solutions
1. You want to support a 50 N weight with your arm bent at 90o.
Draw a free-body diagram and make reasonable estimates of the weight of your
forearm Wa, the length of your forearm and the distance d the biceps ten
Physics 135: Discussion Set # 3
Solutions
1. Consider the picture of the soldier shown.
a) Is the rope stretched in tension or squashed in
compression?
Stretched
b) Is the leg stretched in tension, or squashed in
compression?
T
N
Squashed in compression.
Physics 135: Discussion Set #2
Solutions
1. Consider the human pyramid formed by 10 students all of equal weight W as
shown in figure.
a) Draw a free-body diagram for the student on the top.
How large is the force pushing up on him from below?
Remember, t
Physics 135: Discussion Set #1
Solutions
1.
a) Derive an expression for the radius R of a uniform sphere with density as a function of its mass M.
What is the power law exponent for this relationship?
3M
M V R R
4
3
4
3
1
3
1
3
1
Power Law is R M Expo
Physics 135: Discussion Set # 10
Solutions
1. Your muscles are made of many tiny sarcomers, each of which can give a little tug. A
continuous force is created by having many of these tug and release over and over.
a) Does each little unit do work when it
Physics 135
Discussion #11 Solution
Problem 1: Roller Coaster Physics
Millennium Force (Cedar Point, Sandusky, Ohio) is one of the tallest roller coasters in the
world. As shown in the comparison below, the highest point (A) on the track is 310 ft
94m ab
Physics 135: Discussion Set # 13
Solutions
1. An object oscillates in simple harmonic motion shaking back and forth through 4 complete
cycles every 3 seconds.
a) What is the frequency of oscillation f?
Frequency is cycles/second = 4/3 = 1.33 Hz
b) What is
Physics 135: Discussion Set # 12
Solutions
1. You throw a 5 g piece of gum at a 300 g yoyo at a speed of 20 m/s as shown. How high
does the yoyo swing if the gum sticks to it in a completely inelastic collision?
This has two parts: first the collision, du
Physics 135: Discussion Set # 9
Solutions
1. NASA wants to create a rotating space station in which astronauts walking on the inside of
the ring will feel a normal force between their feet and the floor which mimics the earths
gravity.
a) If the station h
Physics 135: Discussion Set #8
Solutions
1.
A tire 0.5 m in radius rotates at a constant rate of 200 revolutions per minute. Find the speed
and accelerations of a small stone lodged in the tread of the tire (on the outer edge).
2 r
. The period is the tim
Physics 135: Discussion Set # 7
Solutions
1. a) You throw a ball straight up with a velocity of 20 m/s to a friend in the window of an
apartment building at a height of 20 m. How long does it take for the ball to reach her?
y v 0 t 1 gt 2 20 1 gt 2 v 0 t
Physics 135: Discussion Set # 6
Solutions
Motion in one dimension
1. Roll the ball across the floor for about one meter distance. Record the
motion you observe from the initial time when the ball is already rolling
until before you stop it. Call the direc
Physics 135: Discussion Set # 5
Solutions
1. Draw a free-body diagram for the sled. If the sled
contains 200kg of dog food and k = 0.03, with
what force must the dog pull to move the sled at a
constant velocity? Note that the angle between the
rope and th