NECO 2019 - PRACTICAL PHYSICS ANSWER

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ANSWERS:


(1a)
Centre of gravity C G = 50.0cm

(1aviii)
Tabulate:
Under Y(cm): 10; 15; 20; 25; 30;
Under K(cm): 32.7; 35.0; 37.0; 39.0; 41.0;
Under X(cm): 22.7; 20.0; 17.0; 14.0; 11.0;
Under K¹(cm): 29.0; 31.5; 34.3; 36.9; 39.5;
Under X¹(cm): 19.0; 16.5; 14.3; 11.9; 9.5;

(1axii)
(i)i avoided drought by closing the window
(ii)i avoided error due to parallax when reading the meter rule 

(1bi)
Couple is a pair of forces, equal in magnitude, oppositely directed, and displaced by perpendicular distance or moment.

(1bii)
Draw the diagram
Sum of clockwise moment = sum of anticlockwise moment
0.2m = 50 × 0.5
m = 50×0.5/0.2
m = 125g
Mass of beam = 125g



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(3av)
E=3.0v

(3avii)
Tabulate

Under L(cm): 20.0; 30.0; 40.0; 50.0; 60.0; 70.0;
Under I(A): 0.70; 0.60; 0.55; 0.50; 0.45; 0.40;
Under X=E/I(Ohms): 4.2857; 5.0000; 5.4545; 6.0000; 6.6667; 7.5000;

(3aix)
slope = ΔL/ΔX = 66 - 12/7 - 4
= 54/3 = 18cm

Intercept, C

(3ax)
K = 4.9×10^-7
K = 4.9×10^-7 × 18
K = 8.82×10^-6cm/ohm

(3axi)
-I ensured tight connections.
-I avoided error due to parallax on the ammeter.

(3bi)
keep the top or terminals clean.
Do not tighten or remove cables while charging or discharging.

(3bii)
Using ohm's law
R = V/I = 3.5/0.25 = 14ohm







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