mechanics (mass, force, acceleration, work, energy, momentum, velocity) - Category wise Question and Answer Practice Test with Solutions

Answer: (a)

1 light year = speed of light in vacuum × no. of seconds in one year

= (3 × 10⁸ ) × (365 × 24 × 60 × 60) = 9.467 × 10¹⁵ m.

Answer: (d)

It is equal to or less than one.

Answer: (c)

A body moving with a uniform angular velocity ω on a circular path of radius r has radial acceleration equal ω²r directed towards the centre of the path.

Answer: (c)

Answer: (b)

A physical quantity which can be specified completely by giving a single number and the appropriate unit alongside it is known as a scalar quantity. Scalar quantities that have the same physical units can be added or subtracted according to the strict mathematical rules of algebra for numbers.

There are a lot of physical quantities which cannot be described by just a single number of physical units. For example in order to fetch a ball which is thrown it is not only important to know the speed with which it is thrown but also the direction in which it is thrown so that it is easier to locate the ball. Physical quantities which are specified completely by giving a number of units (magnitude) and a direction alongside it are known as vector quantities.

Thus we see that a vector quantity has both magnitude and direction.

Thus, we see that the correct answer to this question is (B).