8th grade Science: Unit 3- Forces and Motion

Forces and Motion

 

General Announcements:

Forces and Motion Webquest- due Monday 12/15

Forces and Motion Quiz #2: Tuesday December 16th
- Newton's 1st law
- Inertia
- Cars lab
- Forces- balanced and unbalanced, Net force

Forces and Motion Quiz #1: Friday December 5th

- Definitions of motion and reference point

- Calculating speed (Speed = distance/time)

- Walk in the Park Lab

- Force definition

Topics:
Forces and Motion Study Guide

Vocabulary	Definition or Formula (with Units)
Motion	Change in position in respect to a reference point
Reference Point	Stationary objects used to compare change in position to
Speed	Distance(m)/Time (sec)
Average Speed	Total Distance (m)/ Total Time (sec)
Velocity	Speed with a direction
Acceleration	m/s2
Inertia	Object’s “laziness”, its resistance to move; the greater the mass, the more inertia
Friction	Force that opposes motion, can result from two surfaces rubbing against each other; can be reduced using lubricants
Newton’s First Law of Motion	An object at rest will remain at rest, unless a force acts upon it, an object in motion will remain in motion, unless a force acts upon it – due to its inertia A.K.A. Law of Inertia
Gravity	Force that pulls objects down to the Earth
Weight	Force due to gravity
Mass	Amount of matter in an object (kg)
Force	A push or a pull; units = Newtons; anything that causes an object to speed up, slow down, or change direction
Balanced Force	Equal forces in opposite direction, doesn’t cause motion
Unbalanced Force	Forces that cause motion, can be in opposite directions or same direction
Net Force	If both forces are in opposite direction, add the two together to get Net Force. If forces are in opposite directions, make the larger force “+” and the smaller one “-“ and then add together.  The object will be moved in the direction of the larger force
Newton’s Second Law	Force = Mass X Acceleration If you increase Force, and keep Mass the same, Acceleration increases. If you keep Force the same and increase Mass, Acceleration decreases.
Newton’s Third Law	For every action, there is an equal but opposite reaction
Spring scale	Instrument used to measure force (Newtons)
Ball and ramp lab	If we increase the height, then the speed of the ball also increases.
Book Pull lab	F=ma As you increase the Mass of the objects, the force needed to move them increases. If you reduce the friction with the addition of the pencils, the force needed decreases.

Links for Forces Webquest:

http://www.physicsclassroom.com/class/newtlaws/U2l2b.cfm#frict  
http://www.bbc.co.uk/schools/scienceclips/ages/10_11/forces_action.shtml
http://www.physicsclassroom.com/class/newtlaws/u2l1d.cfm    
http://science.discovery.com/interactives/literacy/newton/newton.html   
http://www.learner.org/interactives/parkphysics/bumpcars.html    

Additional Information for the Unit:

Newton's Three laws

1st law: Inertia - An object in motion will remain in motion unless acted upon by an outside force, and an object at rest will remain at rest unless acted upon by an outside force.

Inertia is defined as: the tendency of objects to remain in motion or to stay at rest unless acted upon by an outside force.

2nd law: Force - a push or a pull that transfers mechanical energy to an object, sometimes causing a change in the motion of the object.

3rd law: For every action there is an equal and opposite reaction.

Speed and Velocity:

Speed and velocity are very similar, but are not the same.

Speed is defined as the distance that an object travels over a certain amount of time.

The formula for speed is:

Velocity is defined as the distance that an object travels over a certain amount of time AND in a specific direction

The formula for Velocity is:

As you can see velocity is different than speed in that it also requires a direction.

Therefore a change in direction, even though your speed may stay the same, will change your velocity.