CONFIDENTIAL*

Physics 960

Constants value

speed of light in vacuumpermeability of vacuumpermittivity of vacuum

magnitude of electron chargePlanck constantatomic mass unit constantelectron rest massproton rest massmolar gas constantAvogadro constantBoltzmann constantgravitational constantfree fall accelerationcoo

ehumempRL, NAkGg==============3.00 x 108 m s-14 x 10-7 H m-18.85 x 10-12 F m-1[1/(36 )] x 10-9 F m-11.60 x 10-19 C6.63 x 10-34 J s1.66 x 10-27 kg9.11 x 10-31 kg1.67 x 10-27 kg8.31 J K-1 mol-16.02 x 1023 mol-11.38 x 10-23 J K-16.67 x 10-11 N m2 kg-29.81 m s-2

Section A [15 marks]

Answer all questions in this section.

1 Which of the following physical quantities is a scalar quantity?

AVelocityBAccelerationCElectric potential DElectric field strength

2Which of the following physical quantities have the dimensions of ML2T-1 ?

AForceBTorqueCEnergyDAngular Momentum

3 Which of the following errors is a systematic error ?

AZero errorBParallax errorCError due to wrong measurementDError due to non-uniformity of shape

4 The velocity of an object traveling in a straight line changes from 30 ms-1 to 15 ms-1 over a distance of 75 m. Assume that the deceleration is constant. The object will come to rest after traveling an additional distance of

A15 mB25 mC35 mD50 m

5The figure shows a body of weight W placed on a smooth plane inclined at an angle to the horizontal. A force F acts horizontally on the body.

FW

The resultant force acting downwards along the inclined plane isAW cos + F cos BW sin + F cos CW sin - F cos DW sin - F sin

6The maximum and minimum possible resultant forces for two forces acting on a particle are 10 N and 4 N respectively. The magnitudes of the two forces are

A3 N and 7 NB4 N and 6 NC4 N and 10 ND6 N and 14 N

7The diagram shows two trolleys, X and Y, about to collide and gives the momentum of each trolley before the collision.

XY20Ns12Ns

After the collision, the directions of motion of both trolleys are reversed and the magnitude of the momentum of x is then 2 Ns. What is the magnitude of the corresponding momentum of Y?

A6 NsB8 NsC10 Ns D30 Ns

8The gravitational field strength at a point P on the Earths surface is numerically equal to

Athe change in potential energy per unit distance from P.Bthe work done in bringing unit mass from infinity to P.Cthe force acting on any body placed at P.Dthe acceleration of free fall at P.

9Figure shows two stars of equal mass M move with constant speed v in a circular orbit of radius R about their common centre of mass.

What is the net force on each star?

ABCzeroD

10Which of the following statements is true regarding the static friction between two surfaces ?

AStatic friction depends on the area of the surfaces.BStatic friction does not depend on the nature of the surfaces.CStatic friction is always less than dynamic friction.DStatic friction can vary and has a maximum value.

11The graph below shows how the force F between two atoms varies with their separation r.At equilibrium, their molecular separation is

r F z O x yAOXBOYCOZDXY

12.Young s modulus is the ratio of

AForce to extensionBThe energy stored per unit volumeCStrength of the wireDStiffness of the wire

13.The stress-strain graphs for four types of materials are shown below.

Stress Q P R S O Strain

The material that is most stiff is

APBQCRDS

14In the derivation of the equation , which of the following statements is not an assumption of the kinetic theory of gases?

AThe change of momentum of the gas molecules can be neglectBThe intermolecular forces can be neglectedCThe volume of the gas molecules can be neglectedDThe collision between gas molecules is perfect elastic

15The figure below shows the relationship between the average translational kinetic energy a monoatomic molecule of an ideal gas at absolute temperature T.

Tab

The value of Boltzman constant that can be deduced from the graph above is

ABCD

Section B [40 marks]Answer all questions in this section

16A wheel of radius 0.25 m with moment of inertia rotates at 150 revolution per minutes. A tangential force is applied on the rim of the flywheel and its stops after 10 revolutions.

(a) Define angular velocity.

[ 1 mark ]

(b) Determine the initial angular velocity of the flywheel in

[ 2 marks ]

(c) Calculate the angular deceleration.

[ 2 marks ]

(d) Calculate the magnitude of the tangential force

[ 2 marks ]

17(a)Define stress and strain for a stretched wire.

[ 2 marks ]

(b)Draw stress-strain graphs for a brittle material such as steel, a ductile material such as copper and a polymer such as rubber.

[ 2 marks ]

(c) A steel wire of length 2.5 m and cross-sectional 1.5 10-6 m2 is fixed at one end. A load of 10 kg is hung from the free end so that the wire hangs vertically. The Youngs modulus of steel is 2.0 1011 Pa. Calculate

(i) the stress applied

[ 2 marks ]

(ii)the extension

[ 2 marks ]

Section C [30 marks]

Answer any two questions in this section

18(a)(i)State the principle of conservation of linear mementum. [2 marks](ii)State two laws of motion which can be used to deduce this principle in the case of collision between two bodies.[4 marks]

(b)(i)State Newtons Laws of motion [3 marks](ii)What is meant by perfect elastic collision? [1 marks]

(c)A rocket is fixed vertically on its launching pad. Before launching is started, the mass of rocket and its fuel is 1.9 x 103 kg. During launching, gas emitted from the rocket with a velocity of 2.5 x 103 ms-1 relative to the rocket. The fuel is used at the constant rate of 7.4 kg s-1 .(Use g = 10 ms-1)(i) Find the thrust of the rocket.[2 marks](ii) Explain why there is a time lapse between the firing and the launching.[3 marks]

19(a) State the conditions for equilibrium of a rigid body. [1 mark]

(b) A uniform ladder AB of length 2.5 m and weight 200 N leans against a smooth wall as shown in the diagram.

Copy the diagram and show

(i) The reaction R of the wall on the upper end A of the ladder. [1 mark]

(ii) The normal reaction P and the frictional force F at the lower end B of the ladder. [2 marks]

(iii) Calculate the magnitude of R, P and F [3 marks]

(c)

A wooden block on a horizontal table is attached to a pan. As the weights are placed on the pan, tension, T acts on the block, which is balanced by the frictional force F in the opposite direction. The frictional forces is classified into two types; static friction (limiting static friction) and dynamic friction.

(i)What is meant by limiting static friction and coefficient of limiting static friction.[2 marks](ii)Compare the magnitude of limiting static friction and dynamic friction.[1 mark]

(d)The diagram shows a block of mass of 20.0 kg being pulled by a load 10.0 kg. Given that the coefficient of kinetic friction between the block and surface is 0.4. Calculate the acceleration of the block and the tension in the string, assuming the g = 10 m s-2.[5 marks]

20. (a) What is the meaning of (i) internal energy(ii) molar heat capacity for a gas.[ 2 marks]

(b) Describe about internal energy for an ideal gas.[ 2 marks]

(c) Explain why molar heat capacity of a gas at constant pressure is larger than molar heat capacity at constant volume.[ 3 marks]

(d) A quantity of 0.200 mole of gas enters a diesel engine at pressure of 1.04 x 105 Pa and at temperature 300 K. Assuming that it is an ideal gas.(i) find the volume of the gas.[ 2 marks](ii) The gas is then compressed to of its original volume and the pressure is increased to 5.00 x 106 Pa. Find the new temperature of the gas[ 2 marks]

(iii) The gas in d(ii) is supplied with 6000J of heat energy so that it expands at constant pressure 5.00 x 106 Pa, and its temperature rises to 2500K. Find

1. the molar heat capacity at constant pressure.[ 2 marks]

2. the final volume of the gas.[ 2 marks]

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