Transcript Midterm review

Midterm review
Mostly concepts, with a few
calculations thrown in for flavor
Chapter 1 - Units
• What are the three base units we use in this
class for distance, time and mass?
• Meters, seconds, kilograms
• Do we ever use centimeters or grams?
• NO, we do not
• Why Not?
• Because, Dr. Mason, doing so would make all
of the other derived units (such as Newtons
and Watts) come out all wonky.
Ch. 1 - Conversions
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How many centimeters in a meter?
How many meters in a kilometer?
How many seconds in a minute?
How many seconds in an hour?
How many degrees in a revolution (circle)?
Trig Review - 1
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Define sin(θ)
Define cos(θ)
Define tan(θ)
Find all three for the triangle below
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3
θ
4
Trig Review - 2
• In terms of F and θ, FX = ?
• In terms of F and θ, FY = ?
• A force F = 13 N is directed at an angle θ = 400
above the horizontal.
• Find FX
• Find FY
Trig Review - 2
• If I know that the x-component of a force is 4
N and the y-component of a force is 7 N, how
will I find the magnitude of the overall force?
• So then do that.
• How will I find the angle at which the force is
directed?
• So then do that too.
Trig Review - 4
• Which of the following are vector quantities
and which are scalar quantities:
– Force
– Acceleration
– Mass
– Velocity
– Speed
– Time
– Weight
Trig Review - 5
• For the vector quantities in the previous slide,
is there any difference in how you determine
the magnitude or angle (direction) if you have
the x- and y- components?
• This page is too easy. Whoever you are, you
get to do the next slide, too. Everyone else in
the room, cheer for this person for being so
lucky.
Everyone’s favorite problem.
• Little Joey is once again adrift on his sad, sad
little raft. He knows you hate him and his raft,
but begs of you to find his resulting
acceleration anyway. The wind is acting due
east and pushes with 20 N and the current is
at 350 and pushes with 30N. Raft and Joey
have a mass of 200 kg. Find Fx, Fy, F, θ, and a.
The Wile E. Coyote Problem
• Just kidding.
• Instead, resolve these vectors and find the
resultant magnitude and direction of the
acceleration if the mass is 5 kg.
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8
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1-D stuff
• What is the difference between velocity and
acceleration?
• Using your notes/friends, find the following:
– Equation relating distance, time and acceleration
but not speed
– Equation relating distance, time and speed but not
acceleration
– Equation relating speed, time and acceleration but
not distance
– Equation relating distance, speed and acceleration
but not time
More 1-D stuff
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Define ΔV
Define ΔX
What is negative acceleration?
What is negative velocity?
In general, why do we say that g = -9.8m/s2
instead of 9.8m/s2 ?
2-D stuff
• For projectiles, in which direction is motion
constant and in which is it changing?
• Why are they different?
• On the arc below, draw the directions of the
velocity and acceleration vectors in 5 places.
More 2-D stuff
• As a convertible drives along, the passenger
throws a rock vertically upward. Ignoring air
resistance, where will it land?
• Why?
• At what point in the trajectory was the rock
moving the slowest?
• Why?
More 2-D stuff
• A ball is dropped from a height H at the same
instant an identical ball is thrown horizontally
with speed V0 from the same height. Which
hits the ground first? Which has a larger
velocity?
• Explain all that.
More 2-D stuff
• Okay, we’re going to revisit the football punter
problem. V0 = 18 m/s, = 290.
• What info do you use to find the range?
• What info do you use to find the height?
• What info do you use to find the time of
flight?
Forces
• Write out Newton’s 3 laws. Full sentences, not
just the names.
Forces continued
• What is the difference between weight and
mass?
• If all the forces acting on an object = zero, is
the object definitely not moving? Why or why
not?
• What do you call it when all the forces on an
object = 0?
Forces continued
• Two high school students push to the right on
a stalled car. Their individual forces are 340 N
and 280 N. There is a frictional force of 450N
acting on the car. What is the net force acting
on the car?
• If the car’s mass is 1200 kg, what is the car’s
acceleration?
Forces continued
• A man and a moose are standing in the middle
of a frictionless frozen lake. The man’s mass is
90kg, the moose’s mass is 400 kg. The man
pushes on the moose with a force of 110N.
What is the moose’s force on the man?
• What are the individual accelerations?
Forces continued
• What is the difference between g and G?
• What are the values of g and G (including
units)?
• When do you use each (MAKE SURE YOU
KNOW THIS)?
• How do you find the acceleration due to
gravity at the surface of any planet?
Forces continued
• What is the equation for static friction?
• Of static or kinetic friction, which one varies?
• Of static or kinetic coefficient of friction,
which one is usually larger?
• Describe the two step process for solving the
classic “a 10 kg block with coefficients of static
and kinetic friction of 0.43 and 0.37 is pushed
on by a force of…” problem.
Forces continued
• In general, ΣF = ?
• What are the conditions for equilibrium?
• What is your general strategy for solving the
classic “two ropes pull in such and such
direction, what direction does the third rope
have to pull” kind of problem?
Circular stuff
• What is the equation for the circumference of
a circle?
• So, if speed = distance/time, what is the
equation for speed in a circle?
• Find the equation for centripetal acceleration
• Find the equation for centripetal force
• Okay, that’s enough circular motion.
Energy and Work
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What is the formula for work?
What is the formula for kinetic energy?
What is the work-energy theorem?
What is the formula for gravitational potential
energy.
• Explain where this equation for PE comes
from.
Energy and Work
• You have a problem in which the total
mechanical energy is conserved. Write out
explicitly the entire equation you would use to
solve for some quantity (say, the final speed)
and explain this equation to me so that i’m
convinced you understand it.
• In what kind of case is total mechanical energy
not conserved?
Energy and Work
• Explain the difference between conservative
and nonconservative forces.
• Give examples of each.
• What is the formula for power?
• Explain the relationship among power, work
and energy.