Transcript Physics 201/211

Physics 201/211
Physics 201/211
Warm-up Question
A spaceship has a force, F1, acting on it in the +x direction. It also
has two other forces, F2 and F3 acting 120o up and 120o down
from the +x direction, respectively. If the spaceship is traveling at
a constant speed in the +x direction and the magnitude of all the
forces is the same, which statement is true?
A) The spaceship will begin to slow down
B) The spaceship will begin to accelerate downward
C) The spaceship will begin to speed up in the positive y direction
D)The spaceship will begin to speed up in the positive x direction
E) None of the above
Physics 201/211
What must the mass of m3 be to slide m2 out from under m1?
k 
m1=1kg
1
20
m2=3kg
k 
1
10
m3
To go to a football stadium from your house, you first drive 1000m north, then
500m west, and finally 1500m in a direction 20o south of west. (a) relative to
your home, the football stadium is in what direction? How far away is your house
from the stadium in a straight line?
Walking along the beach you notice there is an island at an angle of 30o with
respect to the shore. You then walk 50m along the shore, ending on the other
side of the island. A measure tells you the island is now 40o out from the shore.
How far away is the island from the shore?
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Static Equilibrium
A 1000 kg steel beam is supported by two cables. What is the
tension in each cable?
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A 90 kg man is standing on a scale that determines weight. This
scale is in an elevator that is accelerating in the upward direction.
Will the man’s 90 kg:
A. increase
B. decrease
C. stay the same
Physics 201
Quiz Question
A gerbil runs 85cm in a straight line. This takes it 5s. Then the gerbil turns around
and runs in the opposite direction 65cm. This takes it 3s. What is the magnitude
of the gerbil’s average velocity for the entire trip?
A) 21.7cm/s
B) 17.0cm/s
C) 19.3cm/s
D) 0.25cm/s
E) 0.667cm/s
F) 20.0cm/s
Are two vectors with the same magnitude necessarily equal?
Physics 201
Discussion Question
What is the total distance Δx traveled by the particle?
A) 50m
B) 40m
C) 30m
D) 20m
Physics 201
A father is now three times as old as his son. Twelve years ago he was six
times as old as his son. Find the present age of each.
Physics 201/211
It takes 0.2 second for the back end of a 1500kg
car to crumble within 2m of the front end, in a
collision with an immovable concrete wall. What is
the net force that acts on the front bumper during
this time?
Physics 201
Quiz Question
Which plot represents the velocity vs. time of the particle represented by the
position vs. time graph?
Physics 201
Discussion Question
Below a plot of the position vs. time has been drawn. Draw the corresponding
acceleration and velocity graphs.
Physics 201
Discussion Question
Below a plot of the position vs. time has been drawn. Draw the corresponding
acceleration and velocity graphs.
Physics 201
Quiz Question
Use dimensional analysis to determine what the area under the curve represent?
A) Average Velocity
B) Speed
C) Acceleration
D) Distance traveled
Physics 201
Discussion Question
Below a plot of the velocity vs. time has been drawn. Draw the corresponding
acceleration and position graphs.
Physics 201
Discussion Question
Below a plot of the position vs. time has been drawn. Draw the corresponding
acceleration and velocity graphs.
Physics 201
Quiz Question
Physics 201
Physics 201
Describe what’s happening
What is Fred’s average speed?
What is Brutus’s average speed?
Physics 201/211
Physics 201/211
Describe what’s happening
Physics 201/211
A 90 kg man is standing on a scale that determines weight. This
scale is in an elevator that is accelerating in the upward direction.
Will the man’s apparent weight:
A. increase
B. decrease
C. stay the same
Physics 201/211
a.) How much force does an 80 kg astronaut exert
on his chair while sitting at rest on the launch pad?
b.) How much force does an 80 kg astronaut exert
on his chair while accelerating straight up at 10
m/s^2?
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No Friction
A 10 kg crate is being slid across a frictionless floor by a 40 N force
acting at an angle of 35 degrees below the horizontal. How far will
the crate slide after 10 seconds?
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Friction
a.) A 10 kg crate is being pushed on by a 40 N force acting at an angle
of 35 degrees below the horizontal. What coefficient of static friction
will keep this crate from moving?
b.) If the coefficient of kinetic friction is 10% less than that of static
friction, what will the acceleration of the crate be?
Physics 201/211
Discussion Question
Standing on ice, a father and daughter face each other, pressing flat
hands together. They push off each other and start moving away
from each other. Which of these statements is correct.
A) The daughters acceleration is the same as here fathers
B) Both are decelerating since their push is in the opposite direction
of their motion
C) While in contact their hands are not moving
D)After they push off, both leave with the same speed
E) None of the above
Physics 201/211
Physics 201/211
Physics 201
Discussion Question
What is average velocity of the particle over the time interval Δt=50.0s?
A) 30m/s
B) 0.6m/s
C) 2.0m/s
D) 10m/s
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Find the tension in each
cable and the applied force F
required for that the system
to not move.
Physics 201/211
Physics 201
Discussion Question
Below a plot of the position vs. time has been drawn. Draw the corresponding
acceleration and velocity graphs.
Physics 201/211
What must the mass of m3 be to slide m2 out from under m1?
k 
m1=1kg
1
20
m2=3kg
k 
1
10
m3
Physics 201/211