Homework

Lesson 1 (a-d) 11/14

1. What is Newton's First Law of Motion?
   1. Newton's first law of motion states that "an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an UNBALANCED force
      1. No change in motion unless an unbalanced force acts upon it... otherwise it will move at constant speed in a straight line.
   2. This is referring to two different states: rest and motion.
2. What are inertia and mass?
   1. Inertia is the resistance an object has to change in it's state of motion
   2. Mass is the quantity that is solely dependent on the inertia of an object. A more massive object has a great tendency to resist change in its state of motion.
   3. It measures how difficult it is to change an objects motion (depending on its mass)
3. What is meant by the phrase state of motion?
   1. The state of motion of an object is defined by its velocity (magnitude + direction.)
   2. Therefore, inertia can mean the tendency of an object to resist change in its velocity
   3. OR, the tendency of an object to resist accelerations (when an object is at constant motion)
4. How do balanced and unbalanced forces pertain to Newton's First Law?
   1. If all forces act upon each other remain in equilibrium (as determined by a FBD), then the object will not change its original state.
      1. dynamic equilibrium is at constant speed
      2. static equilibrium is at rest and there is no motion
   2. However, if they are unbalanced (again, determined by a FBD) the object will CHANGE its state.

Lesson 2 (a-d) 11/15

1. What is the meaning of force?
   1. A force is a push or a pull upon an objecting resulting from the object's interaction with another object.
   2. There two categories: contact forces and action-at-adistance forces.
2. What are different types of forces?
   1. Contact forces are the following: frictional, tension, normal, air resistance, applied, and spring force.
      1. frictional: sliding and static friction are the two types; they normally oppose the motion of an object; sliding is when an object slides and static is when objects are at rest and a frictional force still exists between
      2. tension: a pull force on the object
      3. normal: the support force that occurs between an object in contact with another stable object
      4. air resistance: opposes the motion of an object as it travels through the air
      5. applied: force applied by another person or object
      6. spring: compressed or stretched force attached to an object
   2. Action-at-a-distance forces are the following: gravitational, electrical, and magnetic.
      1. gravitational: when a large mass (moon, earth) attracts other objects towards itself; aka weight of the object
   3. So what is the difference between mass and weight?
      1. Weight is the gravitational pull on an object based on mass (N)
         1. Weight= mg (mass times gravity)
      2. Mass is the actual make up of the object (kg)
3. What is a Free Body Diagram?
   1. FBD show the relative magnitude and direction of different forces acting upon a system
   2. These can be used to determine unbalanced and balanced forces
4. How can you determine the net force?
   1. The net force is the vector sum of all the forces that act upon an object
   2. ΣF is the equation for net force

Lesson 3 (a+b) 11/17

1. What is Newton's Second Law of Motion?
   1. Newton's Second Law of Motion states that the acceleration of an object has two components, the mass of the object and the net force of the object.
   2. The equation is a= Fnet/ m.
   3. The acceleration of an object depends directly upon the net force acting upon the object, and inversely upon the mass of the object.
2. Does sustaining motion require a continuous force?
   1. Newtown's Law declares that a constant force is not necessary to keep an object in motion. It is an unbalanced force, per say, friction, that will cause an object to slow; this would demonstrate an application of inertia.

Lesson 3 (Vectors) 12/6

• addition of Forces
  • the goal is to determine the net force
  • head to tail addition of the arrows
  • the net force is not always zero
• Resolution of Forces
  • there can be different components of a force, depending on if there is an angle
  • trigonometric functions can be used to determine the resultant of the force
  • force example, this method could be applied to recreational sailboating
• equilibrium and statics
  • when all the forces acting upon an object are equal, they are said to be in equilibrium (different axises though)
  • horizontal and components
  • The principle is that as the angle with the horizontal increases, the amount of tensional force required to hold the sign at equilibrium decreases
• net forces
  • a force directed at an angle to the horizontal can be resolved into two components
  • together, two components are a replacement for the single force
• tilted surfaces
  • the rate at which an object with slide down an inclined plane is dependent on how steep it is
  • a= gsin(theta)
  • the process of analyzing the forces acting upon objects on inclined planes will involve resolving the weight vector (Fgrav) into two perpendicular components.
• two dimensional diagrams (2 body problems
  • typically involve solving for the acceleration of the objects and the force that is acting between the object
  • examples are trains, Atwoods equations, drop and pull problems

Class Notes

Force

• states that there no change in motion unless an unbalanced force acts on the object
• otherwise it will move at constant speed in a straight line

• property that measures how difficult it is to change an object's motion
• measured by massmass is measured in kg
  • the more mass something has the harder it is to change the motion
• 
  

• a force, is the pull of gravity on a mass
• measured in Newtons (N)
• a = 9.8 m/s/s
• weight can change based on the gravitational pull of the planet
• W= M x g (mass times gravity)

• N=W, then balanced
• Equilibrium (two types)
  • static
    • at rest
    • no motion
  • dynamic
    • constant speed

• when an unbalanced force acts on an object, it will accelerate in the direction of the unbalanced force
• if N > W, a is upward
  • can be velocity and acceleration both going up and in this case you are speeding up
  • if velocity is going downward and acceleration is going up, then you are decreasing speed
    • BOTH have the same direction which is normal being greater than weight

• the difference between two unbalanced forced
• symbol: ΣF