Mid-Yearly Examinations2014___________________

Name: ________________________Grade:__________

GRADE: 10

SUBJECT: PHYSICS TIME: 1 HOURS_______________________________________________________________________________________

Whenever necessary take g = 10 m/s2The use of scientific calculators is allowed.Remember to show all the working and write the units where necessary.

Formulae for Physics

Density = massW = mgPressure = Force volume Area

Moment = F x perpendicular distancePressure = h g

Work done = energy convertedWork = f x d

Power = Energy Time

Exam mark /95Lab Reports /5Final Mark /100

Comments:__________________________________________________________________________

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_______________________________________________________________________________________1. Convert the following quantities in the unit shown in the brackets.

(a) 25200 sec (hrs)7hrs(e) 56.98kg (g) 56980 g

(b) 4.5 ltrs (cm3) 4500 cm3(f) 6.34 m (cm) 634 cm

(c) 36 min (sec) 2160 s (g) 4.5 m2 (cm2) 45000 cm2

(d) 760 mm (m) 0.76 m(h) 6500000 m3(cm3) 6.5 x 1012 cm3 (4)

2. (a) Fill in the gaps below to complete the statement about vector and scalar quantities.

Vectors quantities have size and direction while Scalarquantities have only size. (3)

(b) The table below contains some vector and scalar quantities. Fill in the gaps by choosing two suitable quantities from the list. (2)

VectorsScalars

displacementdistance

forcemass

velocityspeed

Acceleration, momentum, temperature, weightArea, density

List

accelerationAreadensity

momentumTemperatureweight

3. Simon is determining the density of modelling clay by two methods.(a) Method 1 He moulds a piece of modelling clay into a cube shape as shown in Fig1.

Fig 1.(i) On Fig 1, measure the height h, width w and depth d of the cube-shaped piece of modelling clay.

h = 3.4 cm w = 3.2cm d = 3.0cm.

(ii) Calculate the volume of the modelling clay.3.4 x 3.2 x 3.0 = 32.64 cm3 (1)

(iii) Calculate the density of the modelling clay where the mass of the modelling clay is 103 g.

= (2)

(b) Method 2 The student cuts the piece of modelling clay into two pieces. One piece is approximately twice the size of the other piece. The mass of the smaller piece is 34.5 g. Fig.2a shows a measuring cylinder containing water. Fig.2b shows the same measuring cylinder after the smaller piece of modelling clay has been lowered into it.

Fig. 2aFig. 2b

(i) Record the volume of water in the measuring cylinder, as shown in Fig.2a.50 cm3 (ii) Record the new volume in the measuring cylinder, as shown in Fig.2b 64 cm3 (1)

(iii)Describe briefly one precaution you would take to read the measuring cylinder correctly.Measure the volume from the bottom of the meniscus

(iv) Calculate the volume of the modelling clay.64 50 = 14cm3(v) Calculate the density of the modelling clay, where the mass of the modelling clay was 34.5 g. = (1)

(c) (i) Assuming that the experiment has been carried out with care, suggest two reasons why the two values obtained for the density of the modelling clay in (a) and (b) may not be the same.1. Incorrect reading of the mass from the digital balance.2. Parallax errors when reading length, breath and height of the rectangular piece of clay (2)

4. The diagram shows an object hanging on an apparatus that measures weight.

(a) What is the name of the apparatus? Newton Spring Balance (1)

(b) What is the weight of the object shown by the pointer in the diagram? 2.4N (1)

(c) Calculate the mass of the object.Tension

W = mg m = (1)

(d) On the diagram, draw and name the two forces acting on the object. (2)weight

(e) Comment about the size of these two forces.The forces are equal to each other (1)

(f) Which law are you applying to answer the above question? State the law.Newtons third law of motion. For every action there is an equal and opposite reaction. (2)

5. A light spring which obeys Hookes Law is hung from a beam. The lower end carries a pointer which is against the 50mm mark, on a vertical ruler, when the spring has no load attached to it. When a load of 20N is hung on the spring, the pointer moves to the 130mm mark.

(a) Calculate the extension produced by the 20N mass.130 mm 50 mm = 80mm (1)

(b) What load would extend the spring by 1mm?20N = 80mm 20 / 80 = 0.25N ? = 1mm (1)

(c) Where on the scale, would the pointer be when the load attached to the spring is 10N?20N = 80mm800 / 20 = 40mm10 N = ? Thus 50mm + 40mm = 90mm (2)

(d) The following data refers to a stiff mattress spring that is used to suspend very heavy loads.

Force (N)500010000150002000025000

Extension (cm)1.53.04.56.09.0

(i)Use the graph paper provided to plot a graph of force on the y-axis and extension on the x-axis. (3)

(ii) What is the elastic limit of this spring? 6cm or 20000N (1)

(iii)Explain what is meant by elastic limit?The maximum load that the spring can support before it deforms permanently. (2)

6. Fig.3 shows a device used for compressing crushed material.

The lever arm rotates about the hinge H at its right-hand end. A force of 20 N acts downwards on the left-hand end of the lever arm. The force F of the crushed material on the plunger acts upwards. Ignore the weight of the lever arm.

(a) State the law of moments.For equilibrium, the total anti-clockwise moments equal the total clockwise moments (2)

(b) Calculate the moment of the force 20N about the hinge H.Mom = F x d = 20 x 0.5 = 10 Nm(2)

(c) Calculate the upward force F which the crushed material exerts on the plunger.a.c.m. = c.m 10 = F x 0.12 (3)

7. The diagram below shows a triangle that is balanced on one of its vertices.

c.o.g

(a) Mark with a cross the position of the centre of gravity of the above object.(1)

(b) The object is given a slight push. Explain why the triangle will topple over.The downward force of weight comes out of the base area when tilted and so it topples over (2)

(c) In the space below, draw a sketch of the triangle when placed in a stable equilibrium. (2)

(d) What are the two necessary conditions for an object to be stable?The base area needs to be largeThe cog needs to be moved lower down by shifting the weight to the bottom

(e) The figure shows three glass vases containing water. Put the three vases in order of stability.(From the most stable to the least stable)B, C, A (2)

8. A diver is at a depth of 25 m beneath the surface of a lake. He carries a cylinder of high-pressure air on his back.

(a) (i) Explain how the air molecules exert a pressure on the inside surface of the cylinder.The air molecules are moving at high speeds in random direction. They collide with each other and with the walls of the container thus exerting a pressure. (2) (b) (i) The density of the water in the lake is 1000 kg / m3 and the atmospheric pressure at the surface is 1.0 105 Pa. Calculate the total pressure 25 m beneath the surface of the lake. = h g = 25 x 1000 x 10 = 250,000 +100,000 = 350,000Pa (3)

(ii) What happens to the pressure in the lake if the diver had to go down deeper than 25m.The pressure increases as pressure is proportional to depth (1)

9. Trevor uses a pair of roller blades to go roller skating on a Saturday afternoon. Each roller blade has four small wheels as shown in the diagram. While roller skating, the area of each wheel in contact with the ground is 0.04m2.

(a) Define pressure and give its units.Pressure is the force per unit area. Units = Pa and N/m2 (2)

(b) If Trevors mass is 40kg, calculate the pressure that he exerts on the ground when he stands upright with all eight wheels touching the ground.P = (2)

(c) While roller skating, Trevor can balance himself on just one wheel. Calculate a value for the new pressure.P = (2)

(d) If Trevor roller blades on a wooden floor. Will he damage the floor when on eight wheels or when on one wheel. Explain.He will damage the floor when standing on one wheel as the smaller the area of contact the larger is the pressure. (2)

10. Fig. 4 shows some gas contained in a cylinder by a heavy piston. The piston can move up and down in the cylinder with negligible friction.

(a) There is a small increase in the pressure of the atmosphere above the piston.

(i) On Fig. 4, draw a possible new position for the lower face of the piston. (1)

(ii) Explain, in terms of the molecules of the gas and the molecules of the atmosphere, your answer to (a)(i).The atmospheric pressure is now larger than the pressure of the air inside the cylinder thus it exerts a larger force and pushes the piston downwards (2)

(b) The pressure of the atmosphere above the piston returns to its original value, and the piston returns to its original position, as shown in Fig. 4.2.

The gas, piston and cylinder are now heated to a much higher temperature.

(i) On Fig. 4.2, draw a possible new position for the lower face of the piston. (1)

(ii) Explain, in terms of the molecules of the gas and the molecules of the atmosphere, your answer to (b)(i).Pressure is proportional to temperature and so the pressure of the trapped gas increases more than that of the atmosphere and exerts a force and pushes the piston outwards. (2) (c) As a student, youve just experienced a dry dive of 18m at the Hyperbaric Unit ( pressure chamber). Explain what happened to your ears in terms of pressure.As the outside pressure became larger than the pressure inside the ear canal, a pressure was felt on the ear from the outside air. (2)

11. (a) Anna drives an electric car to go to work. She recharges the battery-pack of her car every 80km by connecting the battery-pack to the mains supply.

Complete the following sentences by filling in the missing words from the list below.

kineticelectricalfossilchemical

When the battery of the car is connected to the mains supply, electrical energy is changed to chemical energy. When the car is driven on the road, this energy is changed to kinetic energy. The car does not use fossil fuel from a pumping station. (2)

(b)State one advantage and one disadvantage of each of the following types of energy.

Type of energyAdvantageDisadvantage

Nuclear EnergyLot of energy can be harnessed from a very small sourceLarge expense in safety maintenance

Solar EnergyDoes not polluteLarge areas needed.

(4)

(c) Wind energy is one of the energy sources that can be used for our country.

(i) Is wind energy a renewable or non- renewable source?Renewable (1)

(ii) Name one disadvantage of using wind power.Can be a threat to birds (1)

(iii) Below draw an energy flow chart to represent the energy changes that take place in a wind turbine. sound

electrical

kinetic

(2)

12. An archer pulls the string of his bow, and moves the arrow to the position shown in Fig. 5 He then releases the string so that the arrow is fired towards a target.

(a) The archer does work on the bow.

When is this work done? Tick one box.

as the string is pulled back to the position shown in Fig. 5

whilst holding the string in the position shown in Fig. 5

after releasing the string to fire the arrow (1)

(b) What type of energy is stored in the bow because it is bent?Stored Potential energy (1)

(c) What type of energy does the arrow have because it is moving? Kinetic Energy (1)(d)When the arrow hits the target, the energy changes into Heat and Sound (2)

(e)State the law of conservation of energy.Energy cannot be created nor destroyed. It can be changed from one form to another. (2)

12. A battery drives an electric motor, which turns a pulley to lift a weight of 700N.

(a) Calculate the work done in raising the 700N weight by 200cm.W.D = F x d = 700 x 2 = 1400J (2)

(b) The weight was raised in 2 minutes. Calculate the power of the motor.P = (2)Mid-Year Gr 10 201411