Exam 1: Chapter 3 and 4 Flashcards
What is Newton’s first law of physics?
The law of inertia
What does Newton’s first law state?
It states that a body will maintain in a state of rest or constant motion unless acted on by an external force that changes that state.
What is linear momentum?
Linear momentum is the quantity of motion. It is measured as the product of a body’s mass and its velocity.
M = mv
Will a static object have a momentum?
No, because it is not moving.
Is momentum a scalar or vector quantity?
Momentum is a vector quantity, therefore, it has a magnitude and a direction. It will be able to follow the rules of vector composition and resolution.
What is another name for Newton’s first law of physics?
The principle of conservation of momentum.
What are two types of collisions?
Perfectly ELASTIC impact and perfectly plastic impact.
What is an impact?
A collision characterized by an exchange of a large force during a small time interval.
Explain a perfectly elastic impact.
An impact during which the velocity of the system is CONSERVED. (think bouncy ball).
Explain a perfectly plastic impact.
An impact resulting in the TOTAL LOSS of system velocity. (think pudding).
In most situations, are collisions elastic or plastic?
Neither, they are a combination of both.
What is the coefficient of restitution?
It describes the relative elasticity of an impact. It is typically given as a number that serves as an index of elasticity for colliding bodies.
What is the variable for the coefficient of restitution and its equation?
Coefficient of restitution :
-e = relative velocity after impact / relative velocity before impact
When two bodies undergo a direct collision, the difference in their velocities immediately after impact is proportional to the difference in the velocities immediately before impact.
What was Newton’s second law of physics?
The law of acceleration.
A force applied to a body causes an acceleration of the body of a magnitude proportional to the force, in a direction of the force, and inversely proportional to the body’s mass.
F= ma
If momentum is conserved, how do we add or subtract momentum to a system?
Impulse
What is impulse?
Impulse is a net force acting over some interval of time applied to a system
What is the equation for impulse?
Impulse = force x time = change in momentum
If you were to want to increase momentum, what would you do?
You would either apply more force or apply the force over a longer period of time.
Ex. throwing or striking a ball
If you were to want to decrease momentum, what would you do?
You would apply less force or decrease the period of time
Ex. Safety equipment, catching a fastpitch baseball
What is Newton’s third law of physics?
The law of reaction. For every action, there is an equal and opposite reaction.
When one body exerts a force on a second, the second body exerts a reaction that is equal in magnitude and opposite in direction.
Define work and what is the equation for work?
Work is defined as a force applied against a resistance, multiplied by the displacement of the resistance in the direction of the force.
W = F x d
What are two types of work?
Positive work and negative work.
Explain positive work.
Positive work is when the net muscle torque and the direction of angular motion at a joint are in the SAME DIRECTION.
Example: Pushing the barbell up. You are pushing up, and the barbell is moving up in the same direction.
Explain negative work.
Negative work is when the net muscle torque and the direction of angular motion at a joint are in OPPOSITE DIRECTION.
Example: “Pushing” the barbell as it is going down. You are pushing up on the bar, the barbell is going down in the opposite direction.
What is the units for work?
Joules (J)
What is energy?
Energy is defined as the capacity to do work.
What is mechanical energy?
The capacity to do mechanical work. (Units are the same, Joules (J)).
What is kinetic energy?
The energy of an object or person in motion.
What is potential energy?
The energy that is stored at a particular position (height).
What is a special type of potential energy?
Strain Energy (SE) or Elastic Energy.
What is Strain Energy?
Strain energy is the capacity to do work by virtue of a deformed body’s return to its original shape. (i.e. a spring diving board).
What is the formula for Strain Energy (SE)?
SE = ½ kx2
Where k is the spring constant; representing the material’s relative stiffness or ability to store energy on deformation and x is the distance over which the material is deformed.
Work is equal to what in terms of energy?
The work of a force is equal to the change in energy that it produces on the object acted on it.
W = PE + KE + TE
About how much energy is consumed by muscles into work?
25%
What is impulse?
It is the change in momentum.
To create a large change in momentum, a large force must be applied over a long time.
What is power and what is the formula for power?
Power is the rate of work production.
Work divided by time. P = W / t
Units is Watts (W).
