Forces & Dynamics Unit Notes
Physical Science
Name: ___________________________
Date: ______________ Period: ______
 Force
o
o
o
o
*Force - __________________________________________________________
*Measured in _______________________ or ____________________
Can be measured with a _____________________________________
What forces are being exerted on the football?
 Unbalanced Forces
o In the same direction
 Unbalanced forces that are not ____________ and
________
 The ______________________________ (object accelerates)
 Net force is the overall force acting on an object
o In the opposite direction
 Unbalanced forces that are ______________ and __________________
 The _________________________ (object accelerates)
 When two students are pushing with
___________________________________, a net force occurs
__________________________________________________.
 The net force that moves the box will be the
_____________________________ because they are in
opposite directions.
 Balanced Forces
o When two or more forces act on an object at the ________________
________________________________________________________
o *Balanced Forces - ________________________________________
________________________________________________________
o No change in ________________________
o The net force on the box is zero because the two forces cancel each other.
 Different Types of Forces
___________________
________________

__________/__________
_____________________
_________________ ______________
____________________
_______________&
________________
Normal Forces
o Exists between _________________________ when their surfaces are pressed
together ____________________________________________
o Ex) _________________________________________________
o Ex) ________________________________________________
o Always directed at a ____________________________________!
 Friction & Drag
o Force that _________________________________________________________
o The force on an object always points in a direction ___________________ to the
relative motion of the object
o ______________ causes _______________ energy between objects
o Which direction is the friction?
Pushing
Force
Motion
Friction
o Friction is greater:
 Between __________________________________________

When there’s _____________________________________ (for example
– more weight)
o 3 Types of Friction
 Static Friction - _______________________________________________
____________________________________________________________
 Ex) You push a box but __________________________ because
the static friction cancels the applied force.
 Sliding Friction - ______________________________________________
____________________________________________________________
 Ex) You push a box along a surface. The box continues to move as
_________________________________________
 Rolling Friction - ______________________________________________
____________________________________________________________
 Ex) Car wheels rolling on the road
 Tension
o _________________________________________________________________
_________________________________________________________________
o Tension force always points in the direction of the __________________.
o Tension Practice Problem!!!
 The diagram below shows two people having a tug-of-war. Determine the
unknown tension force.
o T = ___________________
o Tension is constant throughout the entire
rope. Tension is always opposite and equal.
 Air Resistance
o When an object falls, it is pulled down by _________________
o Also pushed up by _____________________________
o The force of air resistance is in the ___________ direction to the force of motion
o Amount of air resistance depends on the ___________, ___________, and
________________ of the object
o If no air resistance is present, then an apple and a feather fall _______________
o Example of Feather and Hammer Falling at the Same Rate because there is no
air on the moon to slow it down from Apollo 15 Mission.
o Watch Video: On the Apollo 15 mission, the hammer and feather fell at the
_____________ rate because there is no ________ on the moon.
 They fell at the same rate because they have a similar _________, not
because of their mass.
 Centripetal Force
o Acceleration towards the ________________________
o Requires an ___________________________________
o Ex) On a roller coaster, the coaster cars zoom around the
loop, the track exerts a centripetal force toward the center
of the loop
o Ex) Bucket of water spun around – water stays in bucket
 Gravitational Force (Weight)
o The ____________________________________________________ exerted on
objects placed in the field
o The field of an object is always there even if the object is not interacting with
anything else
o Gravitational Force is __________________________________________
Fg = _________ x __________
Fg = _____________, m = ______________, g = ________________
o A robot rover used by NASA has a mass of 90 kg.
 What is its mass on Earth?
 Fg = ___________ x ____________________
 Fg = _______________ x ________________
 Fg = _______________ kg m/s2
 On the Moon (gravity is 1/6 less than on Earth)?
 Fg = ___________ x ____________________
 Fg = _______________ x ________________
 Fg = _______________ kg m/s2
o Projectiles and Gravity
o A ____________________________ is anything in motion
o Thrown objects don’t travel in a straight line – __________________________
because of _______________________
o They have ______________ and ________________ motion
o Projectiles follow a _______________________________.
o Gravitational Force Practice Problem!!!
 If the same astronaut stands on the Earth and the Moon their weight is
different.
 Why?
 ___________________________________
___________________________________
___________________________________
 ___________________________________
___________________________________
___________________________________
 Force Diagram Practice Problem #1!!!
o Why does the boy on top of the slide not move but the other boy slides down
easily?
 Force Diagram Practice Problem #2!!!
o The diagram below shows a situation with an unbalanced force. Determine the
type of force and the net force.


Type of Force? ________________________
Net Force?
 Add the individual force vectors that are acting
upon the objects
 (____________) + (____________) = __________, ________
 Newton’s 1st Law of Motion
o *Inertia - _________________________________________________________
__________________________________________________________________
_________________________________________________________
o Watch Video: The gymnast wants to continue running (___________________)
but is stopped by the equipment (___________________.)
 Newton’s 2nd Law of Motion
o *Newton’s 2nd Law - ________________________________________________
__________________________________________________________________
__________________________________________________________________
o The more ______________, the more ___________________!
a = _________________ / ___________________
a = acceleration,
Fnet = force,
m = mass
o Newton’s 2nd Law Practice Problem #1!!!
 Mike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the
car to a gas station, and he makes the car go 0.05 m/s2. How much force
is Mike applying to the car?





Mass = _______________________________
Acceleration = _________________________
F=mxa
F = (_____________) x (_____________)
Answer = _____________________________
o Newton’s 2nd Law Practice Problem #2!!!
 Suppose that the net external force (push minus friction) exerted on a
lawn mower is 51 N parallel to the ground. The mass of the mower is 24
kg. What is its acceleration?





Mass = ______________________
Force = ______________________
F=mxa
(____________) = (___________) x a
Answer = ____________________
 Newton’s 3rd Law of Motion
o *Newton’s 3rd Law - _________________________________________________
__________________________________________________________________
__________________________________________________________________
o “A acts on B so B acts on A”
o For example:
 ____________________________________________________________
____________________________________________________________
 Earth pulls the book down so the book pulls Earth up with an equal force