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2009 WAEC Physics Practical   You are provided with two meter rules and other necessary apparatus. Place one of the...

Physics
WAEC 2009

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  1. You are provided with two meter rules and other necessary apparatus.
  2. Place one of the rules on a knife edge and determine its centre of gravity C. Mark this pos with a piece of chalk.
  3. Read and record the mass M\(_{R}\) of the metre rule written on the reverse side of it.
  4. Attach the mass M= 100g firmly to the rule AB at C using sellotape.
  5. Suspend the metre rule by two parallel threads of length h = 40 cm each at the 10 cm marks. Ensure that the graduated face to the metre rule is facing upwards.
  6. Set the rule AB into a small angular oscillation about the vertical axis through its centre of gravity.
  7. Determine the time, t for 20 complete oscillations. Evaluate the period T and T\(^{2}\)
  8. Read and record the value of d in meters.
  9. Keeping d constant throughout the experiment, repeat the procedure for other values of h = 50, 60, 70, and 80 cm. In each case determine the corresponding values of f T and T. Tabulate your reading. (x) Plot a graph of T on the vertical axis and h on the horizontal axis.
  10. Determine the slope S, of the graph. Evaluate k =s, where Q =2 S, Q 250P
  11. State two precautions taken to ensure accurate results.

(b)i. Define the term couple as it relates to rotational or oscillatory systems.

ii. Give two practical application of a couple in everyday life.

 

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Explanation

Center of gravity C = 49.5cm
Mass of metre rule (MR) = 135g, d = 80cm = 0.8m

h(cm) d(m) t(sec) T=\(\frac{\text{t(sec)}}{20}\) T\(^{2}\)(Sec\(^{2}\))
40 0.8 28.0 \(\frac{28.0}{20}\)=1.40 1.9600
50 0.8 29.0 \(\frac{29.0}{20}\)=1.45 2.1025
60 0.8 31.0 \(\frac{31.0}{20}\)=1.55 2.4025
70 0.8 34.0 \(\frac{34.0}{20}\)=1.70 2.8900
80 0.8 37.0 \(\frac{37.0}{20}\)=1.85 3.4225


Slope (s) = \(\frac{\bigtriangleup {T}^{2}}{\bigtriangleup {h(cm)}}\) = \(\frac{(3.42-0.40)sec^{2}}{(80-21)cm}\)

= \(\frac{3.02sec^{2}}{59cm}\)

= 0.0512sec\(^{2}\)cm\(^{-1}\)

K = \(\frac{S}{Q}\), Q = \(\frac{2}{25d^{2}}\)

K = \(\frac {\frac{S}{2}}{25d^{2}}\)

S = 0.0512sec\(^{2}\)cm\(^{-1}\), d = 50cm = 0.8cm

K = \(\frac{0.0512sec^{2}cm^{-1} \times 25 \times (0.80)^{2}}{2}\)

K = \(\frac{0.0512 \times 25 \times 0.6400sec^{2}cm^{-1}}{2}\) = 0.4096sec\(^{2}\)cm\(^{-1}\)m\(^{2}\)

Precautions: i

- ensured smooth and regular oscillations in a horizontal plane.
- ensured there was no error due to parallax when reading my stopwatch.

(b)i. Couple -This can be defined as two forces of the same magnitude acting in opposite directions but not on the same line.

ii. Practical application of couple include:

- Opening or closing taps.
- Turning a spanner.
- Setting a flywheel in motion about an axis through its center
- Motion of a spinning spindle.
- Riding/pedaling of bicycle

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