Section 1
What is uniform motion?
Uniform motion: an object travelling at a constant rate of motion in a straight line.
The formula for Work is:
And the formula for Force is:
W=Fd (Work=Force x distance)
F=ma (or if we are using acceleration due to gravity F=mg because acceleration due to gravity is a known value of 9.81m/s2)
List seven different forms of energy.
Chemical, electrical, solar, kinetic, heat, mechanical, gravitational potential, nuclear, light, sound.
How do you calculate mechanical energy?
Em=Ep+Ek
What is a Perpetual Motion Machine?
It is a theoretical machine that can keep working forever because there will be no useless energy created. (i.e. is 100% efficient)
Speed is a _______ quantity and velocity is a _______ quantity.
scalar, vector
1)A car moving forward slows down to a stop at a red light. This is an example of __________.
2)When a car is moving backwards and is slowing down to a stop this is an example or ____________.
1) Negative acceleration
2) Positive acceleration
Define:
1) Gravitational Potential Energy
2) Kinetic Energy
3) Mechanical Energy
1) The energy stored in an object at any position above the Earth's surface.
2) The type of energy associated with the motion of an object.
3) The energy due to the motion and the position of an object. (Potential + Kinetic)
For each of the following scenarios give the main energy type:
1)A soccer player kicks a ball across the field.
2)A bungee jumper stands on a high bridge, preparing to leap
3)A car's engine runs on gasoline. When fuel enters the engine’s combustion chamber, a spark ignites it, causing a small explosion.
4) An archer pulls back the string of a bow, preparing to shoot an arrow.
1) Kinetic
2) Gravitational Potential
3) Chemical
4) Elastic
A person is putting their cold hands up close to a warm fire, this is an example of...?
The second law of thermodynamics
A bird is flying 17.0 km/h in a straight line at a constant rate. How long, in hours, will it take the bird to travel 70.0km?
4.12 hours
At t=0 a car has a speed of 30m/s {N}. At t=6s its speed is 14m/s {N}. What is the average acceleration of the car during this time interval?
a= (14m/s - 30m/s)/6s
= -2.7m/s2{N}
A hockey puck has a mass of 3.00 kg. If it is shot at 57 m/s, what is its kinetic energy?
Ek=1/2mv2
= (1/2)(3.00kg)(57m/s)2
=4873.5J = 4.9x103J
A pendulum is swinging back and forth continuously forming a sort of arc, when would it have 1) the most kinetic energy, 2) the most potential energy, and 3) the most mechanical energy?
1) Most kinetic energy would be at the bottom of the arc
2) Most potential energy would be at the top of the arc
3) Most mechanical energy would be throughout the arc
What is meant by efficiency?
It is a measurement of how effectively a machine converts energy input into useful energy output.
How does distance differ from displacement?
Distance: measures the total length of the path traveled by an object, regardless of direction. (is a scalar quantity)
Displacement: measures the change in position; the shortest straight-line distance from the initial position to the final position, including direction. (is a vector quantity)
A bear is initially travelling at a velocity of 17.2 m/s west. If the bears’ average acceleration is 2.25 m/s2 west, it will take _______ s to reach a velocity of 34.5 m/s west.
a=(vf-vi)/t ---> t=(vf-vi)/a
=(34.5m/s - 17.2m/s)/2.25m/s2
= 7.69s
A sparrow has a mass of 7.3kg and is flying at a height of 35m. What is the potential energy of the sparrow?
Ep=mgh
= (7.3kg)(9.81m/s2)(35m)
= 2506.445
= 2.5x103J
How does a pendulum demonstrate the first law of thermodynamics?
A the pendulum swings, its potential energy is converted into kinetic energy and back again, with the total mechanical energy remaining constant.
What are:1) 4 renewable resources and 2) 2 non-renewable resources?
1) Wind, geothermal, tidal, biomass, hydro-electric, solar
2) Fossil fuels and nuclear (nuclear fusion and fission)
Gustav kayaks at an average velocity of 2.7 m/s north for 120s. The he kayaks at an average velocity of 1.3 m/s south for 90s.
a) How far is he from his start point?
b) What is his average velocity for the entire trip?
a) 324m N and 117m S = 324m N + (-117m N)
= 207m N
b) 207m N/(90s + 120s)
= 0.99m/s, N
1) Rearrange kinetic energy formula to find v
2) Rearrange potential energy formula to find m
1) v=sqrt((2Ek)/m)
2) m= Ep/(gh)
A 400g seashell is dropped from a height of 26m. Assuming no energy loss, what was the speed of the seashell before it hit the ground?
Ep=Ek ---> mgh=1/2mv2
v=sqrt(2gh)
= sqrt((2)(9.81m/s2)(26m))
= 22.5858m/s
=23m/s
List the 6 engines and the people that invented them:
1) The Gunpowder Engine- Christiaan Huygens
2) The Steam Engine - Denis Papin
3) The Savery Engine - Thomas Savery
4) The Newcomen Engine- Thomas Newcomen
5) The Watt Engine- James Watt
6) The Internal Combustion Engine- Nicolaus Otto
In applied technology class, Danielle builds a model car powered by solar cells. In direct sunlight, each cell receives 0.917 J of light energy per second and converts this light energy to electrical energy with an efficiency of 12%. What is the useful energy output of the solar cells for each second of operation?
efficiency=(output/input)x100%
output = (efficiency x input)/100%
= (12% x 0.917J)/100%
= 0.11J