Unit notes and practice questions
Everything here is for unit 1 of the Grade 12 Physics textbook: what the chapter covers, the short notes, practice questions with their answers, and the lesson video where one exists.
The cards filed under this chapter on the Grade 12 Physics page. Open one at a time.
When you use it
Use this to relate the apparent brightness of an astronomical body to its luminosity and distance.
Watch out
Apparent brightness decreases with the square of distance, not linearly.
Drafted from Grade 12 Physics, pages 2-24, then checked twice before it went up
| Missile Type | Propulsion | Trajectory | Governing Physics |
|---|---|---|---|
| Cruise missile | Jet-propelled throughout flight | Controlled path | Conservation of momentum |
| Ballistic missile | Rocket-powered in initial phase only | Arc trajectory | Newtonian mechanics and gravity |
When you use it
Use this to contrast the flight phases, engines, and trajectories of cruise versus ballistic missiles.
Watch out
Ballistic missiles carry rocket engines that fire only in the initial launch phase, not throughout the flight.
Drafted from Grade 12 Physics, pages 2-24, then checked twice before it went up
When you use it
Use this to calculate the distance between a radar station and a target from the time taken for the radio pulse to go and return.
Watch out
Always divide the total travel time by 2. The measured time covers the distance to the target and back.
Drafted from Grade 12 Physics, pages 2-24, then checked twice before it went up
| Term | Image Appearance | Echo Property | Body Feature |
|---|---|---|---|
| Anechoic | Black | No sound reflected | Fluid-filled regions |
| Hypoechoic | Dark gray | Fewer sound reflections | Soft body tissues |
| Hyperechoic | Light gray | Many sound reflections | Dense structures |
When you use it
Use this to identify and classify the different shade regions on a medical ultrasound monitor.
Watch out
Anechoic regions appear black because fluids reflect zero echo, not because sound is blocked.
Drafted from Grade 12 Physics, pages 2-24, then checked twice before it went up
10 multiple-choice questions written against this chapter, each with its answer and the reason. Try one before you open the answer.
Question 1
What is the branch of physics that applies physical principles to medical diagnosing and treating abnormal tissues?
Answer: B Medical physics
Why
Medical physics is the branch of physics that deals with the application of physics principles to medical diagnosis and the treatment of abnormal tissues.
Question 2
What is the full form of the acronym RADAR?
Answer: C RAdio Detection And Ranging
Why
The word RADAR comes from the phrase RAdio Detection And Ranging.
Question 3
Which wavelength range corresponds to visible light in the electromagnetic spectrum?
Answer: B About 400 nm to 700 nm
Why
The textbook states that light is electromagnetic radiation in the wavelength region between about 400 nm and 700 nm.
Question 4
According to Newtonian mechanics, when is a standing person in stable equilibrium under gravity?
Answer: A When the center of mass is directly over the base of support
Why
A body is in stable equilibrium under gravity if its center of mass is directly over its base of support. Under this condition, the reaction force cancels the gravitational force and its torque.
Question 5
A radar station in Addis Ababa emits a signal toward an approaching aircraft. The reflected echo returns to the station after 4.0 × 10-5 s. If the speed of light is c = 3.0 × 108 m/s, what is the range of the aircraft?
Answer: B 6.0 km
Why
Using the radar formula R = (c * t) / 2, we get R = (3.0 × 108 m/s * 4.0 × 10-5 s) / 2 = 12000 / 2 = 6000 m = 6.0 km.
Question 6
How does a cruise missile differ fundamentally from a ballistic missile in terms of propulsion?
Answer: A Cruise missiles are jet-propelled throughout their flight, while ballistic missiles are rocket-powered only in the initial phase.
Why
Cruise missiles are jet-propelled throughout their flights, whereas ballistic missiles are rocket-powered only in the initial flight phase and then follow an arc trajectory under gravity and air resistance.
Question 7
In medical ultrasound imaging, why does a fluid-filled region appear black (anechoic)?
Answer: B It does not send back any sound waves (echoes).
Why
Anechoic areas appear black on ultrasound because they do not send back any sound waves (echoless regions), which is typical of fluid-filled regions.
Question 8
Which physical principle do soft-bodied animals such as earthworms and sea anemones utilize to generate body motion without a firm skeleton?
Answer: B Pascal's principle
Why
The textbook states that soft-bodied animals that lack a firm skeleton (such as sea anemones and earthworms) utilize Pascal's principle to produce body motion.
Question 9
How does Magnetic Resonance Imaging (MRI) generate signals from hydrogen protons in body tissue?
Answer: B It disturbs the parallel alignment of protons in a magnetic field using a current pulse, then measures the energy released when the pulse stops.
Why
In an MRI scanner, protons align with a constant magnetic field. A current pulse disturbs this alignment; when the pulse turns off, the protons return to their parallel arrangement and release energy that is detected as an electrical signal.
Question 10
At Entoto Space Observatory, an astronomer compares two identical stars with the same true brightness (luminosity). Star B appears 16 times fainter in apparent brightness than Star A. What is the ratio of the distance of Star B to Star A?
Answer: B 4
Why
According to the inverse square law, apparent brightness ∝ 1 / (distance)2. If Star B is 16 times fainter, its distance must be √16 = 4 times greater than that of Star A.
The app holds 12 questions on this unit, marked as you go. These are the first 10.
Unit 1 runs from page 2 to page 24 of the Ministry of Education edition.
Ministry of Education edition, English, 186 pages
Temari turns this chapter into timed practice and marks it as you go, with an AI tutor to explain anything that did not land.
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