KNEC KCSE Physics Paper 3 – 2014 KCSE COMA Joint Exam

QUESTION ONE
You are provided with the following; -A 400ml glass beaker
– A Bunsen burner
– A thermometer
– A stop watch
– A tripod stand and a measuring cylinder 100ml – A wire gauze
– A source of heat.
Set up the apparatus as shown in the diagram below.

Measure 100cm³ of water and pour it into the beaker. Take the initial temperature of the water.
T0…………………………………………………………………………… (1mk).
Now heat the water to a temperature of 90 ^oC. Switch off the gas tap and place a thermometer into the beaker and start the stop watch when the temperature is 65^o C. Take the temperature T ^oC of water every two minutes.

Record your results in the table below.

(7mks)
(i) Plot a graph of Log (T – TO) against Time (t). (5mks)

(ii) Find the value K of log(T – TO) when t = 0 (2mks)

This question has two parts A and B. answer both parts.
PART A
You are provided with the following:

– A meter rule
– Two identical 100g masses
– About 200ml of liquid L in 250ml beaker
– Three pieces of thread, each about half metre long.

– Stand with clamps
– Tissue paper.
Proceed as follows:
(a) Using a stand and one piece of thread, suspend the metre rule in air such that it balances horizontally.
Record the position of the centre of gravity. G.
G = ________________________ mm
NOTE: The metre rule should remain suspended at this point through out the experiment.
(b) Set up the apparatus as in figure 2 below.

Suspend the mass A at a distance x = 50mm. adjust the position of mass B until it balances mass A
immersed in liquid L.
Record the distance d, of mass B from the pivot.
Repeat the same process for other values of x in table 2 below and complete the table.

(3 mks)

(c) Plot a graph of d (y axis) against x. (5mks)

(d) Determine the slope, S of the graph. (2mks) ………………………………………………………………………………………………………………
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(e) Given S = F/ W , where F is the apparent weight of object A in the liquid L and W is the actual weight of A, find:-
(i) The value of F. (2mks) ………………………………………………………………………………………………………………
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(ii) The upthrust, U (3mks) ………………………………………………………………………………………………………………
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PART B
You are provided with the following:

– A concave mirror with holder
– A screen
– A meter rule
– A candle
– A match box (to be shared)
Proceed as follow:
(f) Set up the apparatus as in figure 3 below.

(g) Put the oblect at a distance u = 30cm from the mirror. Adjust the position of the screen until a sharp image is formed on the screen. Record the distance V.

(h) Repeat procedure (b) above for the distance u = 40cm and record the new distance V. complete the table 3 below.

(2mks)
(i) Given f = V/(m +l) , calculate the values of f hence determine the average value f_av: (3mks) ………………………………………………………………………………………………………………
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