81.The height at which the atmosphere cease to exist is about 80 km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at the height of 20 km above the ground level is?
- A. 380mmHg
- B. 570mmHg
- C. 190mmHg
- D. 480mmHg
82.Ice cubes are added to a glass of warm water. The glass and water are cooled by
- A. conduction only
- B. convection only
- C. conduction and convection
- D. convection and radiation
83.The thermometric substance of an absolute thermometer is
- A. alcohol
- B. mercury
- C. helium
- D. platinum
84.In a Daniel cell, the depolarizer, positive and negative electrodes are respectively
- A. copper sulphate, copper and zinc
- B. manganese dioxide, carbon and zinc
- C. sulphuric acid, lead oxide and lead
- D. potassium hydroxide, nickel and iron
85.A transistor function mainly as a
- A. switch and amplifier
- B. rectifier and an amplifier
- C. charge storer and an amplifier
- D. charge storer and a switch
86.A cell of internal resistance 0.01Ω can be measured accurately using the
- A. Ohm meter
- B. meter bridge
- C. potentiometer
- D. electroscope
87.An electric generator with a power output of 3.0 kW at a voltage 1.5 kV distributes power along cables of resistance 20.0Ω. The power loss in the cables is
- A. 80.0 W
- B. 40.0 W
- C. 10.0 W
- D. 0.1 W
88.The resultant of two forces acting on an object is maximum if the angle between them is
89.A string is fastened tightly between two walls 24cm apart. The wavelength of the second overtone is
- A. 24cm
- B. 16cm
- C. 12cm
- D. 8cm
90.A resistance R is connected across the terminal of an electric cell of internal resistance 2Ω and the voltage was reduced to 3/5 of its nominal value. The value of R is
91.Which of the following metals will provide the greatest shield against ionizing radiation?
- A. Iron
- B. Manganese
- C. Aluminium
- D. Lead
92.Vibration in a stretched spring cannot be polarized because they are
- A. stationary waves
- B. transverse waves
- C. longitudinal waves
- D. mechanical waves
93.A gas at a volume of V₀ in a container at a pressure P₀ is compressed to one-fifth of its volume. What will be its pressure if the magnitude of its original temperature T is constant?
- A. P₀/5
- B. 4P₀/5
- C. P₀
- D. 5P₀
94.A ball is thrown up into the air. At the highest point of its trajectory the ball:
- A. Is accelerating downwards
- B. has zero acceleration
- C. is accelerating upwards
- D. is still moving upwards
95.A ball of mass 200 g moving with a velocity of 8 m/s collides and sticks with another ball of mass 300 g moving in the same direction with velocity 4 m/s. What is the common velocity of the balls after the collision?
- A. 5.6 ms⁻¹
- B. 2.8 ms⁻¹
- C. 11.2 ms⁻¹
- D. 1.4 ms⁻¹
96.A boy holds the end of a rubber cord from which hangs a solid metal ball, if the boy whirls the ball in a horizontal circle, keeping his hand still. If the rubber cord breaks when the ball is at a point on the circle, in what direction will the ball move?
- A. towards the hand of the boy
- B. away from the hand of the boy
- C. in the direction of the tangent to the circle at the point of break
- D. None of the above
97.A force of 20 N applied parallel to the surface of horizontal table is just sufficient to make a block of mass 4 kg set for motion. Find the acceleration when the force is doubled.
- A. 2 ms⁻²
- B. 4 ms⁻²
- C. 5 ms⁻²
- D. 10 ms⁻²
98.A man walks 1 km due east and then 1 km due north. His displacement is
- A. 1 km N15°E
- B. 1 km N30°E
- C. √2 km N45°E
- D. 2 km N75°E
99.A motor car moves with a velocity of 20 ms-1 on a rough horizontal road and covers a displacement of 50 m. Find the coefficient of dynamic friction between the type and the ground (g = 10 ms⁻²)
100.A physics student standing on the edge of a cliff throws a stone vertically downward with an initial speed of 10.0 m/s. The instant before the stone hits the ground below, it is traveling at a speed of 30.0 m/s. If the physics student were to throw the rock horizontally outward from the cliff instead, with the same initial speed of 10.0 m/s, what is the magnitude of the velocity of the stone just before it hits the ground?
- A. 10.0 m/s
- B. 20.0 m/s
- C. 30.0 m/s
- D. 40.0 m/s