In class this week, we talked about energy, work, and power.
Energy is a scalar quantity, which means that it is only measure with
magnitude, no direction. Energy is also conserved in an isolated system, which
means that total Ein=Eout. Energy can be potential
(energy of position), which can be expressed with the equation
PE=(mass)(gravity)(height). Energy can also be kinetic (energy of motion),
which is expressed with the equation KE=1/2(mass)(velocity) 2. The
unit of energy is Joules. Work is a change in energy, and can be written as
W=(force)(distance). The units of work are Newton meters (Nm) or Joule (J).
Power is the rate at which work is being done. Power can be written as
P=∆Energy/∆Time. The units of Power are Joules/Second or Watts.
When I think of potential and kinetic energy, I think of
something falling from a height. The picture below is of me jumping off my bed.
Knowing that my mass is 60kg, and gravity’s pull is 10m/s2,
and assuming my bed is 0.5m high, I can find my potential energy standing on my
bed.
PE=mgh
PE=(60kg)(10m/s2)(0.5m)
PE=300 J
Using my mass, and assuming that when I fell I reached a
velocity of 3.16m/s, I can find my kinetic energy right before I landed.
KE=1/2mv2
KE=1/2(60kg)(3.16m/s) 2
KE= 300 J
