Download Mechanical Energy

January 08, 2015
Mechanical Energy
Energy due to motion and the position of an object.
Mechanical Energy = kinetic energy + potential energy
Em = Ek +Ep
January 08, 2015
Jasmine throws a 0.300kg baseball. At a height of 2.50m it has
a speed of 20.0m/s. What is the total mechanical energy of the
baseball?
January 08, 2015
Think about a Toboggan
At the top of the hill
Em = Ep + Ek
there is no movement.
Em = Ep + 0
Mechanical energy is
So the toboggan's
all potential.
In the middle of the run there is
Em = Ep + Ek
movement and the sled is still above the
surface so the sled has both potential
and kinetic energy.
At the bottom there is
Em = Ep + Ek
no potential energy now
Em = 0 + Ek
surface so all the
because it is on the
potential energy is now
converted to kinetic.
Energy is converted throughout the ride from potential to
kinetic but the total mechanical energy remains the same,
because you cannot create or destroy energy, only convert it
from one form to another.
January 08, 2015
Because Energy isn't created or destroyed we
can say that Ep at the top = Ek at the bottom.
For the hill example.
So Ep = Ek
If an object object has both potential
energy and kinetic energy at the same
time we cannot do this.
E.g you cannot do this 1/4 of the way down the hill.
Because the object will have a little potential energy
left but has a lot of kinetic energy. They will not be
the same.
January 08, 2015
A 50.0 kg athlete jumps vertically upward from the ground
to a height of 0.900m above the ground. What was the
athletes initial vertical speed?
January 08, 2015
Carlynn is falling from the top of a building. Carlynn has a
mass of 50.0kg and she is traveling 5.00m/s right before
she hits the ground. How high was the building?
January 08, 2015
An average force of 100.0N is required to pull back the
bow string a distance of 0.500m. The bow is aimed
vertically.
a) What is the work done on the bow?
b) How much potential energy is stored in the bow?
c) How much kinetic energy does the arrow have at the instant
of it's release?
d) What will the potential energy be at the arrows highest
point?
January 08, 2015
Theron is walking across the balcony when he casually
pushes Cole off of it. If Cole falls 3.05m what is the
velocity right before he hits the ground?
January 08, 2015
Pendulums
January 08, 2015
Problems
Page 183 to 185
# 8 to 14
Page 189
# 1,2,3,4,5,6,7,9
Page 197
#7,8,13,20,21,23,24,25,26,