Material from Midterm 2 to Final Flashcards
(51 cards)
Kinetic energy is energy associated with …
Motion
Potential energy is energy associated with …
Lifting things/gravity.
What does heat deal with?
Transfer of thermal energy.
What does work deal with?
Transfer of mechanical energy.
When is energy conserved in a system?
When the system is isolated from the environment, the energy is conserved.
How can energy be flown into and out of the system?
Via heat (transfer of thermal energy) and work (transfer of mechanical energy).
For the purposes of this class, energy is conserved within a system UNLESS …
Mechanical work is done on it by the environment. ΔEsys=W
What is the equation to keep in mind when dealing with work/kinetic energy?
Fx= Fcosθ=ma(x)
FxΔx= 1/2m(v final)^2-1/2m(v initial)^2
What is the equation for Kinetic Energy?
K=1/2mv^2 (in Joules). 1J= 1kgm^2/s^2
How can the work of something be regarded as if it is opposite the direction of motion?
Negative. ONLY work in the direction of motion is considered positive.
Work on a system results in _____.
A change in Kinetic Energy= ΔK
When something is said to be moving at a constant speed, what is its change in kinetic energy?
- Velocities are not changing, so kinetic energy is 0.
A force applied over some time period changes what value?
mv, being MOMENTUM
Is momentum a scalar or a vector? What are its units?
Vector; has positive and negative signs; units are kgm/s
Define Impulse
Change in an object’s momentum due to a force acting for some time.
Describe Everything about the Conservation of Momentum.
When two objects collide, they have a Newton’s 3rd Law Pair of forces between them. F2 on 1 is equal in magnitude to F1 on 2; their direction is the opposite. The 1st object adds momentum to the 2nd, while the 2nd takes away momentum from the first. SUM OF MOMENTA STAY THE SAME AT ANY GIVEN POINT. Momentum is only conserved when considering ALL the interacting objects.
When is momentum conserved?
When you are considering ALL of the interacting objects in the designated system of choice.
How do we choose the system in which momentum is conserved?
Ideally, we want a system where no external forces are acting on the object. If they are, we can zoom in on the instance where the objects are colliding. In most cases, the resulting force of the collision in that instance will be so large that we can ignore the other external forces.
Define Perfectly Inelastic Collisions
Collisions when objects collide and stick together.
What are some examples of inelastic collisions?
Car crashes-Dog catching a frisbee- Person jumping on skateboard.
What is a key thing to note about inelastic collisions?
Both objects have the SAME final velocity.
In one dimension, what is the equation that involves momentum for inelastic collisions?
m1v1(i) + m2v2 (f)= (m1+m2)vf
With momentum, what are two key things that need to be done?
Define a coordinate system and be mindful of signs.
What happens with explosions?
Objects start at one mass and one velocity and end up with different masses and different velocities.
