# Physics Paper 1 Questions and Answers - Butere Mock Exams 2021

SECTION A (25 MARKS)

1. The figure 1 below shows a scale of a part of a vernier callipers. If the instrument has a zero error of positive 0.03, state the correct reading (2mks)
2. The figure 2 below shows a beaker of height 10 cm and cross – sectional area 25cmfilled with water then inverted over water held in a trough.

The beaker weighs 250g when empty. Determine the amount of force F required to hold the beaker at the position shown. (Take acceleration due to gravity g = 10ms-2 or 10 N/kg, density of water = 1000 Kg/m3) (3mks)
3. The figure 3 below shows a paddle wheel made of light material. Show on the diagram the direction of its rotation when heat is applied at one end of the container as shown.

Below is figure 4 showing a system in equilibrium with a metre rule held horizontally.
Use it to answer questions 4 and 5.
4. PQ is a uniform rule of length 1.0m and weighs 3.0N. Determine the weight of block X. (3mks)
5. Determine the tension in the string AB (2mks)
6. A cyclist of mass 200kg and traveling at 90km/h is involved in a head on collision with a car of mass 600 kg traveling at 110km/h. The cyclist is thrown onto the bonnet of the car which continued to move after impact in the original direction .Find their velocity after impact. (3mks)
A light spring fixed at one end extends by 2.0cm when a weight of 120g is suspended from the free end. Use this information to answer question 7 and 8.
7. Determine its spring constant. (1mk)
8. Three such springs are arranged in a manner shown in figure 5 below and used to support a load. If each extends by 2.0cm, determine the weight of the load. (2mks)
9. An aerial view of a car of mass m moving along a curved part of the road with constant speed is depicted in figure 6 below.

Explain the fact that the car is more likely to slide at Y than at X if the speed is not adjusted. (1mk)
10. A water bucket taking the shape of a sliced off inverted pyramid with a circular base is being filled with water. Explain how its stability varies. (1mk)
11. An object of mass 8 kg is whirled in a vertical circle of radius 2.0m with a constant speed of 6 m/s. Determine the maximum and minimum tension in the string (3mks)
12. A burn from steam is more severe than one from water boiling at the same temperature.
Give reasons. (2mks)

SECTION B (55 MARKS)

1.
1. State Charles’ law for an ideal gas. (1mk)
2. Draw a setup of apparatus that can be used to verify Charles’s law. (2mks)
3. In a similar experiment a student recorded the readings below.
 Temp (ºC) 20 40 60 80 100 Length of air column (cm) 64.5 69 73.3 77.5 82
1. Plot a graph of volume against temperature. (5mks)
2. Use the graph to obtain values for
1. Volume trapped by air at 0ºC. ( 1mk)
2. Temperature at which the volume of the trapped air would become zero (1mk)
2. A ball is thrown vertically upwards with a velocity of 14ms-1. It falls and bounces back with a velocity of 11 ms-1.
1.
1. Represent this information on a velocity – time graph (until it strikes the ground twice) (2mks)
2. Determine the total distance covered until the ball strikes the ground twice. (Assume the ball is thrown from the ground level) (4mks)
2. A tape attached to a moving trolley is run through a ticker timer. Figure 7 below shows a section of the tape after running.

If the frequency of the timer is 100Hz determine the;
1. Average velocity at intervals AB and CD (4mks)
2. Average acceleration of the trolley (4mks)
3.
1.
1. Suggest a reason why some solids change their state directly to gas. (1mk)
2. Presence of wind enhances rate of evaporation of a liquid. Explain how this is achieved. (1mk)
2. The set up in figure 8 below shows some observations made by a form two student in their school laboratory during a physics class. In fig 8(a) bubbles were coming out of water when hydrogen gas was allowed to flow over the porous pot whereas, fig 8(b) shows water having risen through the tube.

1. State what the lesson was investigating. (1mk)
2. Briefly explain each observation made in:
1. Fig 8(a) (1mk)
2. Fig 8(b) (1mk)
3. Name two factors that would affect the observation made in the experiment set up,in figure 8, above. (2mks)
3. A 250 g sample of a solid was heated steadily in a lagged colorimeter of negligible mass.
The observations were represented in a graph as shown below.

1. Explain the shape of the graph. (3mks)
2. The solid requires 12.5J of energy to change its state. Determine its specific latent heat of fusion. (2mks)
4.
1. State the law of flotation. (1mk)
2. A hydrometer of mass 25g floats in an acid of density 1.18 g/cm3 with 3.0cm of its stem above the acid. If the cross- section area of the stem is 0.5cm2, determine its total volume. (4mks)
3. Water flows in a pipe of varying diameter as shown in figure 9 below.

1. Two perforations are developed with time at points A and B as shown. If the holes are of same dimensions, suggest with a reason which hole leaks more. (2mks)
2. If the diameter of the larger end of the pipe in figure 9 above is twice that of its smaller end, find the percentage decrease in speed as the water flows from narrow to wider end. (3mks)
4. Distinguish between streamline and turbulent flow. (1mk)
5.
1.
1.
1. State the law of conservation of energy in terms of kinetic energy and potential energy. (1mk)
2. 210 litres of water is pumped through a height of 20m in 1.2 minutes. Determine the power rating of the pump if it is 75% efficient. (3mks)
2.
1. Draw a pulley system of velocity ratio 5 and having a total of 4 pulleys and explain why its efficiency reduces as the size of the load reduces. (3mks)
2. State the relationship between M.A., V.R and efficiency of a machine. (1mk)

## MARKING SCHEME

SECTION A (25MKS)

Vernier scale 0.08 + 10.68;
-
Zero error + 0.03
10.65cm;
2. Weight of water = mg
= ρ x v x g
= 1000 x 25 x 10 x 10
10000 100
= 2.5N;
Weight of container =  250  x 10
1000
= 2.5N
Total downward force = 2.5 + 2.5 = 5.0 N;
Total upward force = 5N;

3. Convection current set is in anticlockwise direction setting wheel to rotate in opposite direction;

4. (X x 0.4) + (3 x 0.1); = ( 150  x 0.4 x 10);
1000
0.4x + 0.3 = 1.5 x 0.4
X = 0.75N
5. Downward force = upward forces ( tension on AB);
0.75 + 3.0 + .5 = Tension
Tension.
Tension AB = 5.25N;
6. Moment before collision = moment after collision.
200 x 90 x 1000 + 600 x 110 x 1000 = 800v;; Formula substitution
3600                       3600
= 29.167m/s;
7. Spring constant = F/e
= 1.2/2 x 100 = 60 N/m;
8. Weight = 3 x 120
100
= 3.6N;
9. At Y, the radius r is minimum and hence the centripetal force is maximum;
10. As the bucket gets filled, the centre of gravity is raised and so the stability reduces; 1 mk for both pts.
11. T max = mv2 + mg
r
= 8 x 62 + 8 x 10 Formula for both
2
= 224N; Ans
T min = mv2 – mg
r
= 8 x 62 - 8 x 10
2
= 64N; Ans
12. Steam already contains latent heat; (of vaporization) ; which water doesn’t have ;

SECTION B (55 MARKS)

1.
1. The volume of a fixed mass of a gas is directly proportional to its temperature at constant pressure;
2.
3.
1.
• Both axes labelled with appropriate units;
• Simple and uniform scale;
• Correctly plotted point ½ mark each maximum of 4 points
• straight line with positive gradient passing through at least 3 correctly plotted points
2.
1. 60cm ± 0.5;
2. - 268 ± 2º C;
TOTAL = 5MKS
2.
1.

1. Shape of graph
At least 2 peaks
2. h =2
g
Distance = 2 x 142; + 2 x 112;
10           10
= 39.2 + 24.2
= 63.4m
2.
1. Period T = 1; = 0.01s
100
Time AB = 5 x 0.01 sec
Dist = 1.5  m
100
∴vel in AB = 0.015;  = 0.3m/s
0.05;
Time CD = 5 x 0.01 or 0.05s
Distance = 3.2 m or 0.032m
100
Av. Speed CD = 0.032 = 0.64m/s
0.05
2. a = v - u;  formular
t
a = 0.64 – 0.3;
14 x 0.01;  Sub time at
= 2.429m/s 2; ans
V (m/s)
3.
1.
1. Have negligible temperature range in liquid state ;
2. Wind blows out vapour creating room for more evaporation to occur;
2.
1. Effect of density on rate of diffusion:
2.
1. Hydrogen being of lower density diffuse faster inwards than air diffuse outwards;
2. Hydrogen more concentrated inside diffuses faster out;
3.
• Concentration of the hydrogen gas:
• Presence of moving air / wind / draught:
3.
1.
• Between A and B heat is translated to rise temperature with time;
• Between B and C heat is used to break bond between the solid molecules to change state / latent heat;
• Between C and D heat is used to raise temperature of liquid ;
2. Q = mLf
12.5 = 250 LF;
1000
Lf = 50J Kg-1;
4.
1. A floating body displaces its own weight of the fluid in which it floats
2. Volume of acid displaced =   mass   of hydrometer
density
=  25
1.18
= 21.186 cm3
Vol. hydrometer immersed = Vol of acid displaced
= 21.186 cm3
Vol. of part hydrometer = (3 x 0.5) cm3
above acid
= 1.5 cm3
Total volume = 1.5 + 21.186
= 22.686 cm3
3.
1.
• Hole B
• Speed is lower at wider end making pressure to be higher, hence it leaks more;

VA x AA = VB x AB
VA = AB = π x (2r) x 100%
VB    AA      π x r2
= 400% decrease
4. When all the particles passing through a given point or cross – section areas have the same velocity and trace the same path, the flow is streamline whereas when all the particles passing through a given point or cross – section area have differing velocities and trace differing paths, the flow is turbulent
5.
1.
1. The sum of kinetic energy and potential energy is always constant. ;
2.  75p ; = 210 x 10 x 20
100           1.2 x 60
P = 777.8 W;
2.

1. Correct diagram ;
Correct position of Effort and Load ;
As the load reduces, the ration of load to weight of the lower pulleys (and frictional force) reduces hence reduced M.A;
2. Efficiency = M.A  x 100%;
V.R

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