People
In 1896, Henri Becquerel observed that atoms spontaneously degenerate and emit ___________________.
radiation or radiant energy
What type of energy is the result of the vibration and movement of molecules and atoms?
Thermal Energy
What is the formula used to determine gravitational potential energy?
Ep(grav) = mgh
(mass x acceleration due to gravity x height)
or
Ep(grav) = F x d
What is the formula used to determine kinetic energy?
Ek = 1/2 m/v2 (1/2 x mass of object x velocity of object squared)
Mechanical energy is the energy due to the ___________ and ___________ of an object.
the motion and the position of an object
Which individual thought that an invisible fluid (which he called caloric fluid) flowed from hot to cold things.
Thomas Young, Count Rumford or Joseph Black
Joseph Black
As a pendulum bob swings, what type of energy remains constant?
Mechanical Energy
Other than mechanical energy, name two forms of potential energy.
elastic, gravitational, chemical, nuclear
Name two forms of kinetic energy other than mechanical energy.
radiant energy, thermal energy, electrical energy, sound energy
What is the formula for mechanical energy?
Em = Ek + Ep
Em = 1/2 mv2 + mgh
In 1686, after observing Newton's Cradle, what two types of energy did Gottfried Leibniz reason could be observed in nature?
Kinetic Energy and Potential Energy
Break one joule (J) down into smaller units.
J = kgm2/s2
Conservation of Mechanical Energy
At what point in the swing of a pendulum bob has all of the gravitational potential energy been converted into kinetic energy?
Closest to the ground where the pendulum bob swings the fastest.
A bow has just shot an arrow. At what point is the kinetic energy of the arrow equal to the potential elastic energy that was stored in the bow?
At the instant the arrow is released from the bow.
Bob decided to throw his lunch box vertically upward from the ground. It rose to a certain height, and then fell back to the ground (crash).
On a graph plotting Mechanical Energy (Em) of the lunch box as a Function of its Height (m), what would the slope of the best fit line look like?
Horizontal. 0 Slope.
Mechanical energy remains constant.
In 1821, what two types of energy did Thomas Seebeck find a connection between?
Thermal Energy to Electrical Energy.
Name three things that may happen to an object when energy is converted from one form to another.
change in motion, change in position, change in shape, change in temperature
At what point does Ek equal Ep(grav) for a rock falling to the ground from a height?
Just before the rock hits the ground.
An object with the same mass but twice the speed will have ________ times the kinetic energy.
four
A magpie flying horizontally at 4.00 m/s carries a twig (mass of 100 g) in its beak for its nest. Calculate the total mechanical energy of the twig when it is 10 m above the ground.
Em = Ek + Ep
Em = (1/2)(0.100kg)(4.00m/s)2 + (0.100kg)(9.81m/s2)(10m)
Em = 0.800 kgm2/s2 + 9.81 m2/s2
Em = 10.61 kgm2/s2 = 11 J
In 1840, James Joule crashed one block of wood into a second block to demonstrate the connection between what types of energy?
Kinetic Energy and Thermal Energy (which produces heat). The falling block of wood loses kinetic energy as it crashes into the stationary block. The stationary block gains thermal energy in the form of heat.
Name 4 different energy conversions that occur between a fossil fuel and its final conversion into electricity.
Chemical energy in fossil fuel. Thermal energy released during combustion of fuel. Water boils creating steam with kinetic energy. Kinetic energy of steam increases kinetic energy of turbine blades. Turbine turns armature located between a magnet. Induced electrical current produced (electrical energy).
A 2.00 kg box is lifted by an upward force 2.00 m above the ground to the top of a table. What is the gravitational potential energy of the box at this new position?
39.2 J
A 0.500 kg ball is pushed horizontally at a speed of 50.0 m/s. Calculate the kinetic energy of the ball at the moment it starts to move.
625 J
A 2.00 kg rock is dropped over the edge of a cliff, 20.0 m above the ground below. What is the speed of the rock just before it hits the ground?
Ep(top) = Ek(bottom)
mgh = 1/2 mv2 v2 = 2mgh/m v2 = 2gh
v2 = 2(9.81 m/s2)(20.0m)
v = 19.8 m/s