Question

ANSWER ANYY THREE QUESTIONS IN THIS SECTION (60 MARKS
1. (a) State any three characteristic of physicist. (6
marks)
(b) Explain the merits of using SI units for measurement (4
marks)
(c) State the three fundamental mechanical quantities (3
marks)
(d) Copy and complete the Physical Quantity table below. (7
marks)
Physical quantity Units Symbol
Amount of substance ………. Mol
Electric current ……….. A
Length ………… M
Mass …………. Kg
Time Second ……….
………………… kelvin K
Luminous intensity Candela ………………

2. (a) Tabulate four differences between Mass and weight. (8 marks)
(b) State four reliable instrument for measuring the temperature of a body (4 marks)
(c) State three reasons why water is NOT used as a thermometric liquid? (6marks)
(d)State two reasons why alcohol is used as thermometric liquid? (2 marks)
.
3. (a) State three advantages of mercury as a thermometric liquid. (6 marks).
(b) Change 65 to centigrade (4 marks)
(c) Explain the concept ‘’work’’ to your science colleague. (4 marks)
(d) State the principle of Conservation Of Energy (2 marks)
(e) State Isaac Newton First law of motion.

Answer 1

1.(a)

(i) Physicists have a methodical and analytical way to approach problems.

(ii) Physicist believe in more realistic approach than the theoretical one.

(iii) Physicists try to understand the working principle, fundamentals and concept of anything they can think or see. In other words they try to visualize what's really causing behind any phenomenon.

(b)

1. No conversions. The greatest advantage of SI is that it has only one unit for each quantity (type of measurement). This means that it is never necessary to convert from one unit to another (within the system) and there are no conversion factors for students to memorize. For example, the one and only SI unit of length is the meter (m). Numerical prefixes may be attached, but they do not form a separate unit.

2. Coherence. SI units are coherently derived as the simple algebraic quotients or products of a few independent base units, using the same equation as the quantity being measured. There are no numerical definitions or constants for students to memorize. For example, the quantity power is defined as energy per time. Therefore, the SI unit of power (the watt), is defined as the unit of power per the unit of time:

watt = joule per second

In symbols,

W = J/s

3. No fractions. SI uses decimals exclusively, eliminating clumsy fractions and mixed numbers.

4. Prefixes. Prefixes are short, convenient, unambiguous, easy-to-pronounce names and letter symbols for powers of ten, such as kilo (k) for 1 000, mega (M) for 1 000 000, and giga (G) for 1 000 000 000. Prefixes eliminate long, awkward rows of place holding (non-significant) zeroes. Students can master all twenty prefixes very quickly.

A unit with a prefix attached is called a multiple of the unit. It does not form a separate unit! A prefix may be changed by moving the decimal point to get rid of unnecessary zeroes. But this should not be called "converting units" since no arithmetic is involved and the unit remains the same. All that is required is an understanding of place value. For example, rewriting 2 000 m as 2 km is analogous to rewriting 2 000 meters as 2 thousand meters. No arithmetic is necessary. A scientific calculator will move the decimal point automatically, if set to ENG display.

5. Few units. SI has only about 30 individually-named units, most of which are limited to specialized fields. Students can learn the common units in a very short time.

6. Easy to write and say. In general, quantities are much easier to express in SI than in other units. For example, 500 watts (500 W) is much simpler than the many confusing, equivalent, non-SI expressions of power such as 1700 British thermal units per hour (1700 Btu/h), 10 300 large Calories per day (10 300 Cal/d), 120 thermochemical calories per second (120 cal_th/s), 22 000 feet poundsforce per minute (22 000 ft·lbf/min), or 0.142 commercial refrigeration tons.

(c) These are Mass, Length and Time.

(d) Amount of substance ………. Mole
Electric current ……….. A
Length ………… m
Mass …………. Kg
Time Second ……….
Temperature…………… kelvin K
Luminous intensity ..............Candela ………………

2.(a)

1) Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object.

2) Mass is measured by using a balance comparing a known amount of matter to an unknown amount of matter. Weight is measured on a scale.

3) The Mass of an object doesn't change when an object's location changes. Weight, on the otherhand does change with location.

4) Weight depends on the mass while mass doesn't depend on it.

(b) (i) Oral Thermometers

(ii) Forehead thermometer

(iii) Basal thermometer

(iv) Pacifier thermometers

(c) Because-

• It’s thermal expansion is not as linear as other liquids available.
• It’s range of temperatures where it is liquid is very small.
• When it freezes, it expands a lot, breaking the container it is confined in.

(d) (i)Alcohol has a very low freezing point of about −112^oC and hence is suitable in thermometers to record very low temperatures.
(ii) Alcohol has a low boiling point of about 78^oC and therefore cannot be used to measure high temperatures.

3.(a)  (i) Mercury has a high boiling point of about 357^oC and therefore can be used to measure temperatures as high as 357^oC.
(ii) Mercury has a freezing point of about −39^oC and hence is suitable in thermometers to record low temperatures (although not very low temperatures).
(iii) Mercury is opaque and has a shining silvery color of its own, making it clearly visible in the capillary tube of a thermometer.

(b) I don't know if you have given 65 K or 65 F. But it can be three possibilities whether it is 65K, 65F or just 65. Pick one of them according to the question once you've reviewed it again.

If it is only 65 then it can't be converted to centigrade as conversion happens only if they are measurement of the same type of property like temperature here.

if it is 65 K then in centigrad it will be 65 - 273.15 = -208.15^oC

if it is 65 F then in centigrad it will be (65 - 32) x 5/9 = 18.33^oC

(c)

The scientific definition of work differs in some ways from its everyday meaning. Certain things we think of as hard work, such as writing a paper or carrying a heavy load on level ground, are not work as defined by a scientist. The scientific definition of work reveals its relationship to energy—whenever work is done, energy is transferred.

For work, in the scientific sense, to be done on an object, a force must be exerted on that object and there must be displacement of that object in the direction of the force.

Formally, the work done on a system by a constant force is defined to be the product of the component of the force in the direction of motion and the distance through which the force acts.

(d) The principle of conservation of energy states that the total amount of energy remains the same in such conversions, i.e. energy cannot be created or destroyed. In mechanics, the potential energy possessed by a body is frequently converted into kinetic energy, and vice versa.

(e) Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.