What is the SI unit of pressure
Answer: A
The SI unit of pressure is the pascal.
\[1\ \mathrm{Pa} = 1\ \mathrm{N\,m^{-2}}\] It is a small unit - atmospheric pressure is about \(10^{5}\) Pa. The dyne and the newton are units of force, and the joule of energy.
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The absorption of ink by blotting paper involves
Answer: B
Blotting paper works by capillary action.
It is a mesh of loosely packed cellulose fibres with fine pores between them. Ink wets the fibres, so surface tension draws it into the pores, and the narrower the pore the further it is drawn.
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The electromagnetic spectrum includes the following radiations.
I. X-rays II. Gamma rays III. Ultraviolet radiation IV. Visible light
Choose the correct order in increasing order of their frequency.
Answer: D
The order is IV, III, I, II - visible light, ultraviolet, X-rays, gamma rays.
Frequency rises as wavelength falls: visible light at \(10^{14}\ \mathrm{Hz}\), ultraviolet \(10^{16}\), X-rays \(10^{18}\) and gamma rays above \(10^{19}\). Since \(E = h\nu\), the energy and the penetrating power rise in the same order.
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To produce deflection in a television picture tube:
Answer: B
A magnetic field deflects the beam in a television picture tube.
Deflection coils around the neck of the tube sweep the electron beam across and down the screen. Magnetic deflection allows much wider deflection angles than electrostatic plates for the same tube length, which is why an oscilloscope uses plates but a television uses coils.
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An artificial satellite revolves round the earth in a circular orbit. Which quantity remains constant?
Answer: A
Angular momentum remains constant.
Gravity acts along the line joining the satellite to the earth's centre, so it exerts no torque about that centre and \(\vec{L} = \vec{r}\times\vec{p}\) is conserved. In a circular orbit the speed is constant too, but the linear velocity is not, since its direction changes continuously.
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When a body is immersed partly or wholly in a liquid, there is an apparent loss in weight of the body which is equal to the weight of liquid displaced by the body.
Answer: A
True. This is Archimedes' principle.
The apparent loss in weight equals the weight of the fluid displaced: \[F_B = \rho_{fluid}V_{displaced}\,g\] It follows from the pressure being greater at the bottom of the immersed body than at the top.
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One astronomical unit is the average distance between
Answer: A
One astronomical unit is the average distance between the earth and the sun.
It is about \(1.496\times10^{11}\) m, or 150 million km, and light covers it in some eight minutes. It is the natural yardstick for distances inside the solar system: Jupiter is 5.2 AU from the sun and Neptune 30.
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Find the maximum velocity for the overturn of a car moving on a circular track of radius 100 m. The co-efficient of friction between the road and tyre is 0.2
Answer: D
The maximum speed is 14 m/s.
On an unbanked track the friction supplies the centripetal force: \[\frac{mv^2}{r} \le \mu mg \Rightarrow v_{max} = \sqrt{\mu r g}\]
\[v_{max} = \sqrt{0.2 \times 100 \times 9.8} = \sqrt{196} = 14\ \mathrm{m\,s^{-1}}\]
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Temperature can be expressed as derived quantity in terms of any of the following
Answer: D
Temperature cannot be expressed in terms of any of them.
It is one of the seven base quantities of the SI system, alongside length, mass, time, current, amount of substance and luminous intensity. A base quantity is by definition independent of the others and cannot be derived from them.
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Which law is also called the law of inertia?
Answer: A
Newton's first law is the law of inertia.
It states that a body remains at rest or in uniform motion in a straight line unless an external force acts on it, so it defines inertia and identifies the inertial frames in which the other two laws hold.
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