Physics · Paper 2C · 2020

3 questions 🇹🇿 NECTA ✓ Official NECTA answers

CSEE 🇹🇿 NECTA ✓ Official NECTA answers

Physics · Paper 2C · 2020

3 questions

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Questions (3)

Section C

1. 4 marks

Refer to Figure 1 which shows a graph of m$_{1}$ against m$_{2}$ obtained from an experiment.

(a) Clamp a metre rule vertically with the zero mark uppermost. Suspend the spring as shown in Figure 1 using a plasticine. Attach an optical pin to its lower end so that its point will move over the vertical scale. Read and record the scale reading $X_0$. 1 mk

(iv) From the graph determine the unknown masses m$_{1}$ and m$_{2}$ 2 mk

(b) Hang the mass = 50 g, to extend the spring. Read and record the new scale reading hence calculate the extension, $e = X_1 - X_0$ 1 mk

(v) State the physical meaning of the slope S. 2 mk

(c) Without removing the 50g mass and put the unknown mass $m_1$, repeat the procedures in 1(b) for the values of mass $m = 100$ g, $150$ g, $200$ g and $250$ g to obtain a total of five readings, and calculate the extension in each observation. 1 mk

(d) Remove the last 250 g mass and put the unknown mass $m_1$, record the new reading $x_1$ and the corresponding extension $e_1 = X_1 - X_0$ 1 mk

(e) Replace $m_1$ by $m_2$ and repeat the procedure 1(d), record the reading $x_2$ and the corresponding extension $e_2$ 1 mk

(i) Tabulate your results of $m$, $x$ and $e$ 1 mk

(ii) Plot a graph of mass (g) against extension e (cm). 1 mk

(iii) Find the slope S of the graph 1 mk

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2. 14 marks

Determine the resistance per unit length $\rho$ of the wire provided through the following procedures: (a) Set up the circuit as shown in the diagram below, where R is the resistance box, E is a dry cell, K is a key, G is a centre-zero galvanometer, J is a jockey and x is a wire of unknown resistance. (b) Measure the length x of the wire provided equal to 100 cm, fit it to the metre bridge as shown in Figure 2. Close the key and slide a jockey over the resistance wire of the metre bridge until the galvanometer reads zero. Read and record $L_1$ and its corresponding $L_2$ (c) Repeat the procedures in 2(b) without changing the length x, setting R=2 $\Omega$, 3 $\Omega$, 4 $\Omega$ and 5 $\Omega$ and record the values for $L_1$ and the corresponding values of $L_2$ in each case.

(i) Tabulate your results including the values of $\frac{L_1}{L_2}$ 4 mk

(ii) Plot a graph of R against $\frac{L_1}{L_2}$ 4 mk

(iii) Compute the slope of the graph 2 mk

(iv) Determine the value for the resistance per unit length $\rho$ of the wire provided. Show clearly how you arrive to your answer. 4 mk

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