Chapter 3: Causes of Linear Motion Flashcards
Newton’s First Law and what it defines
First law: law of inertia
Resistance of an object to changing motion
The following are examples of which one of Newton’s laws?:
-If no net external force acts on an object: that object will not move if it wasn’t moving to begin with
OR
-It will continue moving at constant speed in a straight line if it was already moving
1st Law: law of inertia
Newton’s First Law: Interpretation
-If an object is at rest and the net external force acting on it is zero, the object must ____ at ____
remain at rest
The product of an object’s mass and its linear velocity
Linear momentum
Describe L=mv
Linear momentum (kg*m/s) = mass (kg) * v which is instantaneous velocity (m/s)
True or false: Linear momentum quantifies current state of motion and resistance to change
True
True or false: All forces between objects are internal forces
True
If velocity of one object in the system increases, velocity of another object ____ to____momentum
decreases, conserve
When two objects in a system collide head on AND separate
-system momentum is conserved
Elastic collisions
When two objects in a system collide head on AND stay together moving at the same velocity
Inelastic
True or false: Most real-life collisions are not perfectly elastic or inelastic
True
What is a means of quantifying how elastic the collisions of an object are?
-ratio between the velocity of separation and the velocity of approach
The coefficient of restitution
What is the difference between the postimpact velocities of two colliding objects called?
Velocity of separation
What is the difference between the preimpact velocities of two colliding objects?
Velocity of approach
Formula for coefficient of restitution
e=v1-v2/u1-u2
Where:
e= coefficient of restitution
v=post impact velocity of each object
u=preimpact of each velocity
True or false: The coefficient of restitution is affected by materials and temperature of colliding objects
True
For perfectly elastic collisions, what is the coefficient of restitution?
1.0
For perfectly inelastic collisions, what is the coefficient of restitution?
0
What is Newton’s Second Law
law of acceleration
What will happen if a net external force is exerted on an object?
-The object will accelerate in the direction of the net external force
-its acceleration will be directly proportional to the net external force and inversely proportional to its mass
Newton’s second law interpreted
-The average net force=mass of an object * the average acceleration of the object
m*a is a cause and effect relationship
-Forces cause acceleration
-Acceleration is the effect of forces
True or false: If a net external force acts on an object, the object accelerates
True
True or false: If an object accelerates, a net external force must be acting to cause the acceleration
True
What is the product of average force and duration of force application?
Impulse
____ causes change in ____of a body it acts on
Impulse, momentum
Mass usually___,impulse changes____
Constant, velocity
True or false: Impulse tells us that we can get the same change in momentum with a large force acting for a short time, or a small force acting for a long time
True
-This is why you should bend your knees when you land, why airbags work and why landing on a pillow hurts less than landing on concrete
3 examples of impulse to increase momentum
Throwing, hitting and push-off
-technique involves increasing duration of force application in a specific direction
3 examples of impulse to decrease momentum
Catching, landing, giving
-Safe performance involves increasing duration of force application to reduce the force magnitude ie landing mats, helmets and footwear
Newton’s Third Law
Law of action-reaction
What happens when an object exerts force on another object?
The other object exerts the same force on the first object but in the opposite direction
True or false: You can think of the third law (law of action-reaction) as the law of equal and opposite
True
Defining the law of action-reaction: for every action, there is and equal and ___ reaction.
There are ___bodies involved when force is exerted
opposite, two
What is it called when the force on each body is the same size but in opposite directions
mirrored pairs
Which law says that all bodies are attracted to one another with a force proportional to the product of their masses and inversely proportional to the square of the distance between them?
-ex: performance on earth (a large mass)
Law of universal gravitation
Formula for Law of Universal Gravitation
F=G (m1+m2/r2)
Where:
F=force of gravity
G=gravitational constant
m1=mass of body 1 (object of analysis)
m2=mass of body 2 (mass of earth)
r= distance between the bodies (radius of earth)
