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Showing 976 to 1000 of 1648 questions (page 40 of 66).

976. In alpha decay, the mass number and atomic number of the nucleus change by

A. -4 and -2 B. -4 and +2 C. -2 and -4 D. -1 and 0 E. 0 and -1

977. The SI unit of radioactive activity is

A. sievert B. becquerel C. gray D. roentgen E. curie

978. Radiocarbon dating of organic remains uses the isotope

A. potassium 40 B. uranium 238 C. carbon 12 D. carbon 13 E. carbon 14

979. Nuclear forces are

A. short range and charge independent B. long range and charge dependent C. identical to electrostatic forces D. effective only between protons E. weaker than gravitational forces

980. The minimum mass of fissile material required to sustain a chain reaction is called the

A. mass defect B. threshold mass C. critical mass D. binding mass E. atomic mass

981. Cobalt 60 is used in medicine mainly as a source of

A. neutrons B. beta particles C. X-rays D. alpha particles E. gamma rays for radiotherapy

982. A radioactive sample of initial activity A0 has a half life T. Its activity after time 4T is

A. A0/8 B. A0/4 C. A0/2 D. A0/16 E. A0/32

983. The dimensional formula of Young's modulus is

A. [M0L0T0] B. [ML-2T-1] C. [ML2T-2] D. [ML-1T-2] E. [MLT-2]

984. A set of measurements that are closely grouped but far from the true value is described as

A. both accurate and precise B. accurate but not precise C. free from systematic error D. neither accurate nor precise E. precise but not accurate

985. A vernier scale has 10 divisions coinciding with 9 divisions of a main scale graduated in millimetres. The least count is

A. 0.1 mm B. 0.05 mm C. 0.01 mm D. 0.9 mm E. 1 mm

986. Which of the following pairs does not have the same dimensions?

A. frequency and angular velocity B. force and energy C. work and torque D. stress and pressure E. impulse and momentum

987. If the rectangular components of a vector are equal in magnitude, the vector makes an angle with the x-axis of

A. 30 degrees B. 0 degrees C. 90 degrees D. 60 degrees E. 45 degrees

988. The magnitude of the vector 3i + 4j - 12k is

A. 13 B. 19 C. 5 D. 7 E. 12

989. The torque of a force about an axis is zero when the line of action of the force

A. acts at the rim B. is parallel to the displacement C. passes through the axis D. has maximum magnitude E. is perpendicular to the axis

990. The single force that balances a set of concurrent forces is called the

A. couple B. normal reaction C. component D. resultant E. equilibrant

991. For two vectors A and B, the relation between A x B and B x A is

A. A x B = 2 B x A B. A x B = -B x A C. they differ in magnitude only D. they are equal E. both are zero

992. Newton's third law action and reaction forces

A. are unequal in magnitude B. occur one after the other C. act on the same body and cancel D. act on different bodies and do not cancel E. act in the same direction

993. Newton's first law of motion gives the definition of

A. inertia B. force C. impulse D. momentum E. weight

994. A body is projected at 10 m s-1 at 60 degrees to the horizontal. Its horizontal component of velocity is

A. 8.66 m s-1 B. 10 m s-1 C. 5 m s-1 D. 6.5 m s-1 E. 2.5 m s-1

995. When two bodies of equal mass collide elastically in one dimension, they

A. move with the same velocity B. reverse direction with doubled speed C. both come to rest D. exchange their velocities E. stick together

996. In a perfectly inelastic collision, the quantity that is not conserved is

A. total energy B. mass C. charge D. linear momentum E. kinetic energy

997. A projectile launched at 45 degrees with a speed of 10 m s-1 has a horizontal range of about

A. 20.4 m B. 10.2 m C. 5.1 m D. 1.02 m E. 15.3 m

998. The weight of a body at the equator compared with its weight at the poles is

A. slightly less B. greater C. doubled D. the same E. zero

999. The work done by a variable force is obtained from a force displacement graph as

A. the length of the curve B. the intercept on the force axis C. the slope of the graph D. the maximum ordinate E. the area under the graph

1000. The orbital speed required for a satellite in a low Earth orbit is about

A. 1.6 km s-1 B. 29.8 km s-1 C. 7.9 km s-1 D. 3 km s-1 E. 11.2 km s-1

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