Formulas
Net Force
Conceptual
Forces and Friction
Free Body Diagrams
100
What is our standard force equation (AKA Newton's second law of motion)?
F=ma
Force= mass x acceleration
100
What do we do to forces that are acting in the same direction?
You add the forces together.
Ex: 5 N to the right, 12 N to the right
Fnet= 5 N +12 N; Fnet= 17 N to the right
100
How do we determine the net force acting on an object?
Fnet = F1 + F2 + F3 +...
100
What does tripling our net force do to the acceleration of an object?
The acceleration is also tripled.
100
What is the net force in the free body diagram?
Fnet = 17 N to the right
200
Which formula would we use to determine the mass of an accelerating object undergoing a force?
mass= Force/acceleration or
m= F/a
200
What do we do to forces acting in opposing directions?
We subtract these forces.
Ex: 65 N north, 78 N south
Fnet= 65 N + (-78 N); Fnet= 13 N south or -13 N
200
Which direction do frictional forces act?
Friction forces act in the opposite direction of an object's motion.
200
What would happen if an object traveled on a frictionless surface?
The object would continue to travel forever, unless it comes into contact with another object.
200
Determine which of the following forces are balanced, and which ones are unbalanced.
a) Unbalanced
b) Balanced
c) Unbalanced
300
Determine the force of a 23.8 kg bear is encountering as it undergoes an acceleration of 2.3 m/s2.
F=ma
F= (23.8 kg)* (2.3 m/s2)
F=55 N
300
Determine the net force of the following scenario:
A manager at a sushi restaurant is applying 38 N forward to a box on the ground. The friction that results is determined to be 18 N.
Fnet = F1 + F2
Fnet= 38 N + (-18 N)
Fnet = 20 N
300
What is the net force of an object that is traveling at a constant velocity?
F= 0 N
An object at constant velocity means it has zero acceleration.
300
Name five examples of friction.
Kinetic, static, rolling, sliding, fluid
300
Label what each force in the free body diagram represents.
F10 N (top) = Normal force
F20 N = Applied force
F15 N= Friction force
F10 N (bottom) = Force due to gravity
400
The Death Star is undergoing a forward force of 756,000 N through an asteroid field. The asteroids contact the Death Star in the opposite direction of its motions with a combined force of 13000 N. What is the acceleration of the Death Star if its mass is 509,000 kg?
F=ma --> a=F/m
F=Fforward+ Fasteroids
F=756000 N + (-13000 N)= 743000 N
a= 743000 N/ 509000 kg
a=1.5 m/s2
400
Determine the net force of the following scenario.
Two students are moving a refrigerator. They attach a rope to the fridge. They pull on the left with a combined force of 388 N. The force of tension is determined to be 45 N, and the friction created by the pulling of the fridge is 63 N.
Fnet = Fapplied + Ftension + Ffriction
Fnet = 388 N + (-45 N) + (-63 N)
Fnet = 280 N
400
What value do we use for the acceleration due to gravity?
a= -9.8 m/s2
400
Say we have a skater moving with a force of 563 N. If the net force of the skater is 304 N, what would be the rolling friction the skater encounters?
Fnet = Fapplied + Ffriction
Ffriction = Fnet - Fapplied
Ffriction = 304 N - 563 N
Ffriction = -259 N
400
Draw a free body diagram for the following scenario:
A force is applied to the right to drag a sled across loosely packed snow with a rightward acceleration. Neglect air resistance.
Mr. Gomez will check the students' free body diagrams. The following forces should be present
Normal force (upward)
Force due to gravity (downward, arrow same size as Normal force)
Applied force to the right
Friction force to the left with a smaller arrow than the applied force
500
What type of relationship is between acceleration and mass?
Inversely Proportional
500
Determine the force of the following scenario:
A skydiver is free falling, and has a mass of 84 kg. Once they activate their parachute the force of the skydiver is reduced to 300 N. What is the force of the skydiver's free fall if they have a net force of -523 N?
Fnet = Ffree fall + Fparachute
Ffree fall = Fnet - Fparachute
Ffree fall = -523 N -300 N
Ffree fall= -823 N
500
What does Newton's third law of motion state?
For every action, there is an equal and opposite reaction.
500
What is the relationship between static and kinetic friction?
Static friction applies to objects not moving. Once the static friction is overcome by an applied forces, the kinetic friction is present. As one of type of friction increases, the other will decrease.
500
Draw the free body diagram for the following scenario:
A college student rests a backpack upon his shoulder. The pack is suspended motionless by one strap from one shoulder.
Mr. Gomez will check the students' free body diagrams. They should contain the following forces:
Tension force: upward
Force due to gravity: downward, arrow same size as tension