Physics

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Showing 726 to 750 of 1648 questions (page 30 of 66).

726. The Paschen series of hydrogen lies in the

A. visible region B. ultraviolet region C. X-ray region D. infrared region E. microwave region

727. Stimulated emission differs from spontaneous emission in that the emitted photon is

A. emitted in a random direction B. in phase and in the same direction as the incident photon C. of lower energy D. unpolarized E. of longer wavelength

728. The relation between the decay constant and the half life is

A. lambda = T B. lambda = T/0.693 C. lambda = 0.693/T D. lambda = 1/T2 E. lambda = 2T

729. In positron emission, the atomic number of the nucleus

A. decreases by 4 B. increases by 1 C. decreases by 1 D. increases by 2 E. is unchanged

730. Control rods in a nuclear reactor are made of materials such as boron or cadmium because they

A. reflect neutrons B. conduct heat well C. produce neutrons D. slow down neutrons E. absorb neutrons strongly

731. Nuclear fusion requires extremely high temperatures in order to

A. melt the fuel B. increase the nuclear force range C. reduce the mass defect D. overcome the electrostatic repulsion between nuclei E. ionize the surrounding air

732. Radioisotopes are used in agriculture mainly to

A. trace the uptake of nutrients by plants B. reduce the need for water C. sterilize soil completely D. replace fertilizers E. increase rainfall

733. How many base units are defined in the International System of Units (SI)?

A. 9 B. 5 C. 8 D. 7 E. 6

734. The dimensions of Planck's constant are the same as those of

A. angular momentum B. linear momentum C. power D. energy E. force

735. A screw gauge has a pitch of 0.5 mm and 50 divisions on its circular scale. Its least count is

A. 0.001 mm B. 0.01 mm C. 0.05 mm D. 0.025 mm E. 0.5 mm

736. Which of the following is a supplementary unit in SI?

A. mole B. kelvin C. newton D. joule E. radian

737. The dimensional formula of pressure is

A. [ML-3T0] B. [ML-2T-2] C. [ML-1T-2] D. [ML2T-2] E. [MLT-2]

738. If a quantity is measured as 4.0 cm with an absolute uncertainty of 0.1 cm, the percentage uncertainty is

A. 4% B. 0.4% C. 25% D. 2.5% E. 0.25%

739. A dimensionally correct equation

A. is always physically correct B. may still be physically incorrect C. always contains a trigonometric term D. must be numerically correct E. cannot contain constants

740. A unit vector perpendicular to the plane containing vectors A and B is given by

A. (A x B)/|A x B| B. (A.B)/|A||B| C. A + B D. A - B E. A.B

741. The value of i . (j x k) is

A. j B. i C. -1 E. 1

742. Two forces of 10 N each act on a body with an angle of 120 degrees between them. The magnitude of the resultant is

A. 17.3 N B. 14.1 N C. 0 N D. 20 N E. 10 N

743. If A + B = A - B, then vector B must be

A. a null vector B. equal to A C. a unit vector D. parallel to A E. perpendicular to A

744. Torque is defined as

A. r + F B. r . F C. r x F D. F x r E. F . r

745. For a body in complete equilibrium, the number of independent conditions that must be satisfied is

A. 1 B. 5 C. 3 D. 2 E. 4

746. The scalar product of two mutually perpendicular vectors is

A. maximum B. zero C. unity D. equal to their cross product E. negative

747. A vector of magnitude 10 units makes an angle of 30 degrees with the x-axis. Its y-component is

A. 8.66 units B. 7.07 units C. 10 units D. 2.5 units E. 5 units

748. Newton's second law of motion provides the definition of

A. action and reaction B. force C. inertia D. mass E. momentum

749. The SI unit of impulse is equivalent to

A. J s B. kg m s-2 C. kg m s-1 D. N s-1 E. N m

750. In a perfectly elastic collision, which quantities are conserved?

A. momentum and mass only B. momentum only C. kinetic energy only D. momentum and kinetic energy E. kinetic energy and mass only

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