Energy & work in mechanics Flashcards
(20 cards)
What is kinetic energy?
The energy an object possesses due to its motion
How much kinetic energy would an object have when it is stopped?
0
What is gravitational potential energy?
The energy stored in an object based on its mass and height above a surface
Describe each variable in E=1/2mv2
E= the kinetic energy (J) m= mass (kg) v= velocity (speed) (meter/sec)
If a bus weighs 10 000Kg travels at 50km/h how much kinetic energy does it have?
Ek= 964660.5 J
If a bus weighs 10 000Kg and its kinetic energy is 980KJ then how fast was it going? (m/s and km/h)
14m/s
50.36km/h
Describe the variables in Ep=mgh
Ep= Potential energy (Joules) m= mass (Kg) g= gravitational field intensity (Earth=9.8m/s2) h= height above the surface (m)
If a car weighs 10 000Kg and is dropped from a 1km distance, how much potential energy would you absorb if you were hit?
Ep= 98 000 000 J
What does Em mean?
Mechanical energy
How much work you do is related to what?
How much energy is required to move an object over a certain distance
Describe the variable in W=(F)(delta d)
W=work (J)
F= force (N)
delta d= distance (m)
If it took 50KJ to push a desk 5 meter across the floor, what force was required to do it?
N= 10 000N
What is equal to the change in total mechanical energy?
The total amount of work you do
Total energy= Ek+Ep
Movement of objects horizontally is what type of energy?
Kinetic
Movement of objects vertically is what type of energy?
Potential
Describe the variables in F=mg
F=force (N)
m= mass (KJ)
g=gravity (m/s2) or (N/kg)
What is the weight of a person whose mass is 50Kg on Earth?
F=490N
Describe mass
- Mass is our weight on Earth.
- The amount of stuff (atoms) that make us up
- DOES NOT CHANGE no matter what planet we are on
Describe weight
- Is dependent on the force or pull of gravity on you
- CAN CHANGE on a different planet or moon
Do we weigh less on the moon?
yes. less gravity
