Chapter 3 - Linear Kinetics Part 1 (Week 2) Flashcards
(23 cards)
What is Newton’s first Law of motion?
Law of inertia
What does the law of inertia state?
“If no net external force acts on an object, that object will not move if it was not moving, or it will continue moving at constant speed in a straight line if it was already moving.
Based on newton first law, what happens to an object at rest and in motion if no other forces act on them?
Objects at rest will stay at rest
- objects in motion will stay in motion
R = W = 10lbs. What does R and W mean?
W = weight is the force due to gravity
R = normal force or reaction force
What are the forces in holding a 10lb dumbell?
gravity and your reaction force
According to newton first law, what happens if an object is at rest with zero net external forces?
Object must stay at rest
According to newton first law, what happens if an object in motion with zero net external force
Must continue moving at a constant velocity in a straight line
What is the net external force if an object is at rest?
Must be zero
What is the net external force if an object in motion is at constant velocity in a straight line?
Must be zero
What is inertia?
Resistance of an object to a change in its sate of motion, assuming mass is constant
OR
How resistance an object is suseptidle to change
What is linear momentum?
is a measure of an object’s motion - How much motion it has based on its mass and velocity
What does these variable mean? L = mv
L = Linear momentum
m = mass
v = instantaneous velocity
“L = constant if ∑F = 0” What does this mean?
L refers to linear momentum or angular momentum
- if no external force acts on a system, then its total linear momentum stays constant
What is elastic collision and inelastic collision?
Elastic collsion:
- momentum is conserved
- kinetic energy is also conserved
Inelastic collsion:
- momentum is conserved
- Kinetic energy is not conserved
What is kinetic energy?
Is the energy of moton
*if an object is moving, it has kinetic energy, the faster or heavier, the more kinetic energy
What does it mean when kinetic energy is conserved?
The total amount of kinetic energy before and after an event or collision stays the same
In a perfectly ineleastic collision (also called Perfectly plastic collision) what happen to the object in terms of momentum, kinetic enegy, and the two objects itself?
- momentum is conserved
- Kinetic energy is not conserved
- the objects stick together after colliding (like football)
What is the coefficient of restitution (COR)?
COR written as e, is a number that tells you how “bouncy” a collision is (or in other words how much kinetic energy is conserved in the bounce)
What is the equation for coefficient of restitution?
e = relative speed after collision/ relative speed before collision = v2 - v1 / u1 - u2
u = initial velocity
In a COR equation, if the final valuse is close to 1, what does the object tell you? what about close to 0?
1.0 = bouncier
0.0 = less bouncy or no bounce?
What value is e when the collision is perfectly inelastic?
e = 0
- no bounce occurs
- momentum is still conserved
What is the equation to measure balls dropped on a fixed ground?
e = square root bounce height/drop height
