Download Newton`s Laws Study Guide w Torque - Ms. Gamm

Newton’s Laws
Physics Spring Semester
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Name:
Per.
This exam will cover all of the topics described below. It is worth approximately 250 points. Study your
homework, reading logs, notes and labs. The textbook chapters covered are 4, 5 and 8.
You will be allowed to use a scientific calculator, the equation handout and a 3 x 5 notecard.
The exam will be on Tuesday, March 19th
A. Newton’s 1st Law
 State Newton’s 1st Law
 Define force and inertia and what factors affect each
 Draw a FBD for different situations (identify and label all forces involved).
 Be able to calculate accelerations, masses and forces for different situations
B. Newton’s 2nd Law
 State Newton’s 2nd Law
 Explain freefall using Newton’s 2nd Law
 Explain what a Newton is identify the different units of force
 Explain the difference between weight and mass
 Write equation for Fnet = sum of all F acting in the x or y direction w/appropriate signs (+/-)
 Understand if the net force is zero, an object continues to do what it was doing. If it was not
moving it will stay still. If it was moving at 10 m/s it will continue to move at 10 m/s.
C. Newton’s 3rd Law
 State Newton’s 3rd Law
 Be able to identify the action force, reaction force, and effects of both for given situations
D. Friction
 Define friction
 Explain the variables that affect the strength of frictional force
 Be able to draw the location and direction of friction on a FBD
 Know when to use the kinetic vs. static coefficient of friction
E. Torque
 Explain what torque is and how to calculate it
 Explain rotational equilibrium
 Define center of mass and know where it is located in objects with uniform mass
 Be able to calculate torques, masses and forces in situations that have rotational equilibrium
Vocabulary
 Mass
 Weight
 Inertia
 Normal force
 Weight force
Name
Force
mass
weight
acceleration
Coefficient of friction
1.
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Variable
Friction
Tension
Applied Force
Net force
Acceleration
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Unit
Constant speed
Coefficient of friction
Terminal velocity
Skidding
Gliding / sliding
Unit abbreviation
kg
N
Fw or Fg
Meters per second per second
None
none
If the box in the diagram is moving with constant horizontal velocity, what is true about the relationship between F friction and Fapplied?
2.
If the box in the diagram is accelerating to the right, what is true about the relationship between F friction and Fapplied?
3.
If an object is sitting on a horizontal surface and not accelerating in the vertical direction, what must be true about the relationship
between the upward- and downward-pointing forces?
4.
The given diagram shows an object that is doing what?
5.
According to Newton’s 2nd Law, how are acceleration and force related? How are acceleration and mass related?
6.
According to Newton’s 3rd Law, when a truck’s windshield exerts a force on a bug, what other force happens at the exact same
moment? How big is this other force? Why does the bug splatter, but the truck’s motion doesn’t seem to change?
7.
A 700kg race car accelerates uniformly from rest to 32m/s over a distance of 30m. What size net force causes this acceleration?
8.
What is the weight of a 28kg object on Earth?
9.
If a 10kg object were tied to a rope and accelerated upward, what force would have to be applied to the rope to accelerate the object
upward at 5m/s2?
10. What horizontal applied force would be needed to pull a blue whale of mass 1.9x105kg with constant velocity along a horizontal floor,
if the coefficients of static and kinetic friction between the whale and the floor are, respectively, 0.35 and 0.16?
11. A worker moves a 100kg crate horizontally by pulling on a rope attached to the crate. He pulls with a straight horizontal force of 400N.
If
between the crate and ground is 0.35...
Find the acceleration of the crate. 12. A 55kg boy and a 40kg girl use a rope while engaged in a tug-of-war on an icy frictionless surface. If the acceleration of the girl
toward the boy is 2.1 m/s2, determine the magnitude of the acceleration of the boy toward the girl.
13. A 19kg box is being pulled across a horizontal frictionless surface by a 90N force, directed at 27o above the horizontal. What is
magnitude of the component of force that is pulling the box forward? What is the box’s acceleration?
14. The 500N crate in the diagram is being pulled at a constant velocity to the right. Find the coefficient of kinetic friction between the crate
and ground.
Answers: 1) They must be equal. 2) Fapp is larger than Ffriction. 3) They must be equal. 4) The object is either at rest or moving at a constant speed. (It’s definitely NOT
accelerating.) 5) Acceleration and force are directly related. Acceleration and mass are inversely related. 6) The bug exerts a force on the windshield. The force on the
windshield is equal in magnitude to the force on the bug. Though the forces are equal, the accelerations are not equal. The bug has such a small mass, it undergoes a very
large acceleration.7) 11,947 N, 8) 274.4 N
9) 148N, 10) 297,920 N, 11) 0.57 m/s 2, 12) 1.53 m/s2 13) 80.19N, 4.22 m/s 14) 0.442 11) 0.57 m/s2