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Physics
WAEC / WASSCE 1996
Mechanics and Properties of Matter
Solution
(a) Define the apparent cubic expansivity of a liquid
(b)(i) Describe with the aid of a labelled diagram, an experiment to determine the apparent cubic expansivity of a liquid.
(ii) State two precuations that should be taken to ensure accurate results.
(c) A density glass bottle contains 44.25g of a liquid at 0^\circC and 42.02g at 50^\circC. Calculate the real cubic expansivity of the liquid. (Linear expansivity of glass = 1.0 x 10-5K\(^{-1}\))
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a) The apparent cubic expansivity of a liquid is defined as the apparent increase in volume per unit volume per unit rise in temperature.
(b)(i)
Procedure: Density bottle dried and weighed, M,, fill bottle with liquid, replace the stopper and wipe the bottle dry. Weigh bottle and content M\(_2\), suspend the bottle with content in a water bath. Record the initial temperature of the water in the bath T\(_1\). Then heat water gradually up to boiling point. Notice that some liquid is expelled through the orifice of the stopper and the water in the bath is allowed to continue boiling until no more liquid is expelled through the orifice of the stopper.Record the final temperature T\(_2\) of the water bath. Remove the bottle from the bath, allow it to cool, wipe, dry it and reweigh M\(_3\).
Calculation: Mass of the liquid expelled from the bottle = (M\(_2\) - M\(_3\)) Mass of the liquid left in the bottle = (M\(_3\) - M\(_1\) Temperature change, (T\(_2\) - T\(_1\)) Apparent cubic expansivity
\(\alpha\) a = \(\frac{\text{Mass of the liquid expelled}}{\text{ Mass of remaining liquid \times change in temperature}}\)
\(\alpha\) a = \(\frac{M_2 - M_3}{(M_3 - M_1) - (T_2 - T_1)}\)
(ii) Precautions;
(1) Avoid parallax in reading thermometer
(2) Bottle should not be submerged
(c) Apparent cubic expansivity
\(\alpha\) a = \(\frac{M_2 - M_3}{(M_3 - M_1) - (T_2 - T_1)} = \frac{44.25 - 42.02}{42.02 \times 50}\)
\(\alpha\) a = 1.06 x 10\(^{-3} k^{-1}\)
But real cubic expansivity = \(\alpha\) a =+ \(\alpha\) g
Where \(\alpha\) g is the cubic expansivity of the containing vessel i.e. glass
\(\alpha\) a = 1.09 x 10\(^3 K^{-1}\)
Source: Myschool Past Questions Archive (Record #54740)
Physics
WAEC / WASSCE 1996
Mechanics and Properties of Matter
Solution
(a) Explain what is meant by the statement: The capacitance of a parallel-plate capacitor is 2\(\mu\)F
(b) State: (i) three factors on which its capacitance depends
(ii) three uses of capacitors.
(c) Derive a formula for the energy W stored in a charged capacitor of capacitance C carrying a charge Q on either plate.,
(d) Two parallel-plate capacitors of capacitances 2\(\mu\)F and 3\(\mu\)F are connected in parallel and the combination is connected to a 50V d.c. source. Draw the circuit diagram of the arrangement and determine the:
(i) charge on either plate of each capacitor
(ii) potential difference across each capacitor
(iii) energy of the combinad capacitors.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
3(a) This means that the ratio of the charge on the capacitor to the potential difference between the plates is 4LF.
(b)(i) (1) Area of plates
(2) Dielectric between plates
(3) Distance between plates
(b)(ii) (1) To separate a.c from d.c.
(2) To control current in a.c circuit
(3) To store charges or energy
(c) Workdone, W = QV
Average work done is given by \(\frac{1}{2}\) x QV .........(i)
But V = \(\frac{Q}{V}\) ...............(ii)
Substituting (ii) in (i)
W = \(\frac{1}{2}\) x Q x \(\frac{Q}{C}\)
Energy stored W = \(\frac{1}{2} \times \frac{Q^2}{2} \frac{1}{2} \frac{Q^2}{C}\)
(i) Q\(_2 = C_2V\)
= 100 x 10\(^{-6}\) C = 100\(mu\)C
\(Q_1 = C_1 V\)
= 3 10\(^{-6}\) x 50 = 150\(\mu\)C
(iii) P.d across each capacitor is 50V
(iii) E = \(\frac{1}{2} CV^2\) Since capacitors are in parallel
C = \(\frac{1}{2}\) x 5 \(\mu\)F x 50 x 50
= \(\frac{1}{2}\) x 5 x 10\(^{-6}\) x 50 x 50 = 6.25 x 10\(^{-3}\)J
Source: Myschool Past Questions Archive (Record #54742)
Physics
WAEC / WASSCE 1996
Mechanics and Properties of Matter
Solution
(a) Explain the following terms:
(i) viscosity;
(ii) terminal velocity.
(b)(i) Describe an experiment to determine the terminal velocity of a steel ball falling through a jar of glycerine..
(ii) State two precautions that should be taken to ensure accurate result.
(c) State two
(i) effects of viscosity
(ii) applications of viscosity.
medium Difficulty
Verified Correct Answer: Option
Physical Principles & Numerical Solution
(a)(i) Viscosity is the property of a fluid which tends to prevent or oppose motion of one layer or part over another. It varies with the temperature and nature of the fluid. (ii) A body falling through a fluid eventually attains a steady velocity called terminal velocity. At this point the weight of the body equals the upthrust and viscous force. (b)(i)
Description: A tall glass jar is filled with glycerine anJ supported vertically. Bands (acting as markers) are attached to points A.B.C.D.E and F at equal intervals. The ball is allowed to fall from the top of the jar while the time is noted as the ball passed each marker in turn. It will be observed that the time intervals between A and B, B and C are different while the time intervals for C and D, D and E, E and F are equal. Showing that a steady terminal velocity is reached from C. This ;Weans that
\(\frac{CD}{t} = \frac{DE}{t} = \frac{EF}{t}\) is the terminal velocity.
(ii) Precautions:
(1) Drop the ball gently.
(2) Ball must fall centrally down the glycerine
(c)(i) (1) Viscosity is responsible for the different rates of flow of fluid
(2) Viscosity affects motion of bodies in fluids.
(ii) (1) Viscous liquids are used as lubricants
(2) The knowledge of viscous drag is applied in the design of ships and aircraft.
Source: Myschool Past Questions Archive (Record #54743)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
A body of mass 7.5 kg is to be pulled up along a plane which is inclined at 30o to the horizontal. If the efficiency of the plane is 75%, what is the minimum force required to pull the body up the plane?
(g = 10ms-1)
A
5.0 N
B
20.0 N
C
50.0 N
D
75.0 N
E
200.0 N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25056)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
A machine has an efficiency of 60%. If the machine is required to overcome a load of 30 N with a force of 20 N calculate its mechanical advantage?
A
0.7
B
0.9
C
1.5
D
2.5
E
10.0
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
Mechanical Advantage = \(\frac{Load}{Effort}\) but Load = 30N and Effort = 20N
M . A = \(\frac{30}{20}\) = 1.5
Source: Myschool Past Questions Archive (Record #25061)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
A body of specific heat capacity 450J kg-1 K-1 falls to the ground from rest through a vertical height of 20m. Assuming conservation of energy, calculate the change in temperature of the body on striking the ground level. (g = 10ms-2)
A
0oC
B
2/9oC
C
4/9oC
D
9/4oC
E
9/2oC
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25065)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
An air bubble of volume 2 cm\(^3\) is formed 20m under water. What will be its volume when it rises to just below the surface of the water if the atmospheric pressure is equivalent to a height of 10m of water?
A
6cm3
B
4cm3
C
3cm3
D
2cm3
E
1cm3
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
P\(_1\)V\(_1\) = P\(_2\)V\(_2\)
When the bubble comes to the surface and pressure drops 3 times, the volume increases 3 times.
V\(_2\) = 3 x 2
= 6 cm\(^3\)
Source: Myschool Past Questions Archive (Record #25067)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
The pressure of a given mass of gas changes from 200 Nm2 to 100 N m2, while its temperature drops from 127oC to - 73oC. Calculate the radio of the final volume of the gas to its initial volume.
A
2.4:1
B
2.0:1
C
1.2:1
D
1.0:1
E
1.0:2
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
To find the ratio of the final volume of the gas to its initial volume, we use the ideal gas law:
\(\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}\)
Rearranging gives:
\(\frac{V_2}{V_1} = \frac{P_1 T_2}{P_2 T_1}\)
Substituting the values:
- \( P_1 = 200 \, N/m^2 \)
- \( P_2 = 100 \, N/m^2 \)
- \( T_1 = 400.15 \, K \)
- \( T_2 = 200.15 \, K \)
We have:
\(\frac{V_2}{V_1} = \frac{200 \times 200.15}{100 \times 400.15}\)
Calculating the ratio:
\(\frac{V_2}{V_1} = \frac{40030}{40015} \approx 1.0:1\)
Thus, the ratio of the final volume of the gas to its initial volume is: 1.0:1
Source: Myschool Past Questions Archive (Record #25068)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
What is the escape velocity of a body on the surface of the earth of radius R if the gravitational constant is G and the mass of the earth is M? (Neglect energy losses to the surroundings)
A
2GR
B
2G/R
C
2GR2
D
\(\sqrt{\frac{2GM}{R}}\)
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
Set initial total energy to zero:
\(\frac{1}{2}mv^2 - \frac{GMm}{R} = 0\)
\(\frac{1}{2}mv^2 = \frac{GMm}{R}\)
\(v^2 = \frac{2GM}{R}\)
\(v = \sqrt{\frac{2GM}{R}}\)
Source: Myschool Past Questions Archive (Record #25087)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
A charge of 1.6 x 10-10C is placed in a uniform electric field of intensity 2.0 x 105NC-1. What is the magnitude of the electric force exerted on the charge?
A
3.2 x105N
B
1.8 x105N
C
3.2 x10-5N
D
1.8 x10-5N
E
4.0X10-6N
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option C.
Source: Myschool Past Questions Archive (Record #25088)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
A balloon containing 546cm3 of air is heated from 0oC to 10oC. If the pressure is kept constant, what will be its volume at 10oC?
A
526cm3
B
546cm3
C
556cm
D
566cm3
E
819cm3
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
No expanded working has been attached for this question yet. The verified answer is Option D.
Source: Myschool Past Questions Archive (Record #25089)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
A capacitor of capacitance 25\muF is connected to an a.c. power source of frequency 200 Hz. Calculate the reactance of the capacitor
A
0.01
B
0.02
C
50.00
D
100.00
E
200.00.
medium Difficulty
Verified Correct Answer: Option D
Physical Principles & Numerical Solution
To calculate the reactance of a capacitor, we use the formula:
\(X_C = \frac{1}{2 \pi f C}\)
Given: C = 25\(\mu\)F = 25 \(\times 10^{-6}\), F = 200 Hz
Substituting the values into the formula, we approximate \( \pi \) as 10:
\(X_C = \frac{1}{2 \times 10 \times 200 \times (25 \times 10^{-6})}\)
Calculating this: \(X_C = \frac{1}{2 \times 10 \times 200 \times 25 \times 10^{-6}} = \frac{1}{0.01} = 100 \Omega\)
Thus, the capacitive reactance is: 100\( \Omega\)
Source: Myschool Past Questions Archive (Record #25094)
Physics
WAEC / WASSCE 1995
Mechanics and Properties of Matter
Solution
The energy stored in a capacitor of capacitance 5\muF is 40J. Calculate the voltage applied across its terminals?
A
4000V
B
200V
C
16V
D
6V
E
4V
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
\(E = \frac{CV^{2}}{2}\)
\(V^{2} = \frac{2E}{C}\)
\(V^{2} = \frac{2\times 40}{5 \times 10^{-6}}\)
\(V^{2} = 16 \times 10^{6}\)
\(V = 4 \times 10^{3} = 4000v\)
Source: Myschool Past Questions Archive (Record #25095)
Physics
UTME / JAMB 1995
Mechanics and Properties of Matter
Solution
Which of the following is the dimension of pressure?
A
ML-1T-2
B
MLT-2
C
ML2T-3
D
ML-3
medium Difficulty
Verified Correct Answer: Option A
Physical Principles & Numerical Solution
Pressure = heg
= m x \(\frac{kg}{m^3}\) x \(\frac{m}{5^2}\)
= ML-1T-2
Source: Myschool Past Questions Archive (Record #27748)
Physics
UTME / JAMB 1995
Mechanics and Properties of Matter
Solution
What is the acceleration due to gravity 'g' on the moon, if g is 10-2 on the earth?
A
0. 10 ms-2
B
0.74ms-2
C
1.6ms-2
D
10.00ms-2
medium Difficulty
Verified Correct Answer: Option C
Physical Principles & Numerical Solution
s = 10-2 on earth
g = 6 ms-2 on earth
Earth on moon = \(\frac{10}{6}\)
= 1.6ms-2
Source: Myschool Past Questions Archive (Record #27758)