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For more information, please see full course syllabus of Physical Science
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Lecture Comments (2)

0 answers

Post by Yisrael Harris on May 2, 2013

Why is there no air resistance in a non-falling moving object?

0 answers

Post by Francisco Gonzalez on October 25, 2011

I love the way this teacher explains each topic.


  • Force – a push or a pull
  • Net force – total of all forces on an object
  • Balanced forces – balanced forces means that the net force = zero
  • Unbalanced forces – unbalanced forces on an object cause the object to move in the direction of the larger force or the net force. Unbalanced forces cause the acceleration of the object.
  • Friction – force that brings objects to a stop.
  • Static Friction-two surfaces in contact are prevented from sliding past one another – must overcome this force to begin moving a stationary object.
  • Sliding Friction-brings a sliding object to a stop due to contact of two surfaces.
  • Rolling Friction-force between surface of wheel and surface that the object is rolling on.
  • Air Resistance – A frictional force between air molecules and a falling object – the larger the surface area of the falling object, the larger the force of the air resistance.
  • Fluid friction – force between an object and a liquid.
  • First Law of Motion – an object at rest will stay at rest and an object in motion will stay in motion unless an outside force acts upon it.
  • Second Law of Motion – acceleration of an object is in the same direction as the net force.
  • Third Law of Motion – for every action force, there is an equal and opposite reaction force.


What unit is used to measure force?
The motion of an object changes when forces are ______.
What is said about the forces when the net force on the object is zero?
The forces are balanced and the object is not changing direction.
How do you calculate the net force on an object when the forces are pushing and pulling in the same direction?
Add the forces
What force brings all objects to a stop?
What type of friction is present between a car at rest and the ground it is resting upon?
Static friction
Which of Newton's laws of motion is also known as the law of inertia?
The first law of motion
According to Newton's second law of motion, if the force applied to an object is a push from left to right, in which direction will the object accelerate?
To the right
According to Newton's third law of motion, if the force you apply to the ground while standing still is 450N down, what is the force the ground is applying to you?
450 N up
You and your bumper car together have a mass of 240kg. The momentum of the bumper car that runs into you and stops is 480 kg x m/s. At what velocity will you be traveling after the collision?
Your velocity will be 2 m/s

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.



Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Force 0:04
    • Force Definition
    • Net Force
    • Balanced Forces
    • Unbalanced Forces
    • Forces Examples
  • Friction 7:53
    • Friction Definition
    • Static Friction
    • Sliding Friction
    • Rolling Friction
    • Fluid Friction
    • Air Resistance
  • Newton's Laws of Motion 14:06
    • First Law of Motion
    • Inertia
  • Newton's Laws Continued 17:13
    • Second Law of Motion
    • Third Law of Motion
  • Gravitational Force 24:17
    • Gravity and Gravitational Force
  • Example 1: Horizontal Force, Frictional Force, and Net Force 28:36
  • Example 2: Net Force and Acceleration 29:38
  • Example 3: Gravitational Force 30:35
  • Example 4: Force of Air Resistance and Net Force 32:32