Grade 11 – Physics

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Nuclear Engineering
Thermal Hydraulics and Safety Analysis

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Physics

◦ Attempts to explain and predict interactions between matter and energy
◦ Tiny: subatomic level – neutron, proton, electron and photon
◦ Gigantic: super macroscopic level – meteor, planet, stars and the universe.

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Why is Physics important?

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Two Models from
Aristotle

◦ Movement of the objects on Earth

 Four elements or essences: earth, water, air and fire.
 A rightful place for all elements ◦ Movement of the stars

 Fifth essence
 Invisible sphere – supporting the celestial bodies 

Galileo and Scientific Inquiry
◦ Earth and other planets orbit around the Sun in our solar system.
(Primitive Telescope)
◦ Conducted Experiment: Objects falls at the same rate

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Thinking Scientifically
◦ Theory: brain storming, collect ideas

◦ Model: a representation of the phenomena
◦ Observation: gather information qualitatively or quantitatively. 

Framing A Problem

◦ Organize information: Bullet form, sketches, written text etc.
◦ Understand the problem: know what the problem is asking you.

◦ Solve the problem: formulate a way to solve the questions asked.
◦ Review your answer: check the answer against the problem see if the answer make sense.

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Significant Figures
◦ We can count exactly; however, we can not measure exactly ◦ If we are measuring the height of a table, then the height could be different when it is measured by different people.

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Significant Figures
◦ The last digit of the height is VERY important
◦ 62.4 has 3 significant digits
◦ 0.0310 has 3 significant digits as well, and it should be written in 3.10 102

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SO WHAT! WHY IS PHYSICS AND ALL THESE
IMPORTANT?
◦ Tacoma Narrow Bridge

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Center of Weight
◦ The four different picture shows four different kinds of motion

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Frame of Reference
◦ Relative to the observer

◦ A pedestrian sees a car which is moving forward pass by him.
The driver sees the pedestrian which is moving backward pass by him.

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Relative Motion
◦ Sitting in a car while viewing outside
◦ Sitting in a car while viewing the driver
◦ Unaware the motion relative to the ground (in a car or in a commercial airliner)

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Relative Motion (cont.)
◦ Sudden stop of a car

◦ Car Accident
 Smashing against a brick wall  Smashing against another coming traffic which travels at the same speed

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Distance and Displacement
◦ Displacement (regarding the initial and final position)  Vector (magnitude and direction)

◦ Distance (regarding the path of movement)
 Scalar (magnitude only)

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Symbols
◦ If one object travels back to the initial position, then the displacement equals 0

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EX1.
◦ Determine the 3 displacements between
Freda’s home and the other three buildings
 Home to school
 141m

 Home to diner
 200m

 Home to sports complex
 360m

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EX1: (Cont.)
◦ What is the total distance and displacement if Freda goes to school, dinner, then sports complex everyday?  Total Distance
 700m

 Displacement
 360m

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EX2:
◦ Dawn starts from zero, and bikes 2km east, then
3km west. (a) Draw a vector diagram, and (b) find her final position.

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EX3:
◦ Dawn starts from 0 again, but this time she goes
2km north and then 3km east, (a) Draw a vector diagram and (b) find her final position.

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Velocity
◦ The rate of change of position.
◦ Displacement over changing time.

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EX4:
◦ Does speedometer of a car provide speed or velocity?  Speed

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EX5:
◦ A student runs around a 400m oval track in 80s.
Would the average velocity and average speed be the same? Explain?
 Depends – if the student stopped at the initial position, then the average velocity is actually 0

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EX6:
◦ A dragster in a race is timed at the 200.0m and
400.0m points. The time are shown on the stopwatches in the diagram. Calculate the average velocity for a) the first 200.0m, b) the second
200.0m and c) the entire race.

a)50.0m/s[E]
b)33.3m/s[E]
c)40m/s[E]

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Constant Velocity
◦ Velocity is not changing