Practice Mechanics work and energy - general science mcq Online Quiz (set-2) For All Competitive Exams
Q-1) In case of negative work the angle between the force and displacement is
(a)
(b)
(c)
(d)
Q-2) A particle is moving in a circular path of radius r. The displacement after half a circle would be
(a)
(b)
(c)
(d)
Q-3) Two teams are pulling a rope with equal and opposite forces each of 5 kN in a tug of war so that a condition of equilibrium exists. What will be the tensile force in the rope?
(a)
(b)
(c)
(d)
Q-4) When a stone tied to a string is whirled in a circle, the work done on it by the string is
(a)
(b)
(c)
(d)
Q-5) How much time will it take to perform 440 J of work at a rate of 11 W?
(a)
(b)
(c)
(d)
Q-6) A couple produces a
(a)
(b)
(c)
(d)
Two forces equal in magnitude but opposite in direction form a couple which tends to rotate the body.
Q-7) The energy of wind is
(a)
(b)
(c)
(d)
Q-8) When you compress a coil spring you do work on it. The elastic potential energy
(a)
(b)
(c)
(d)
Q-9) ML2T –2 are dimensions of
(a)
(b)
(c)
(d)
Moment of force = r × F = [L] [MLT–2] = [ML2T–2]
Q-10) A vector quantity is a physical quantity which needs
(a)
(b)
(c)
(d)
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).
Q-11) A man is at rest in the middle of a horizontal plane of perfectly smooth surface of ice. He can move himself to the shore by making use of Newton’s
(a)
(b)
(c)
(d)
Q-12) The numerical ratio of average velocity to average speed is
(a)
(b)
(c)
(d)
It is equal to or less than one.
Q-13) If a ship moves from freshwater into seawater, it will
(a)
(b)
(c)
(d)
Q-14) A person is sitting in a car which is at rest. The reaction from the road at each of the four wheels of the car is R. When the car runs on a straight level road, how will the reaction at either of the front wheels vary?
(a)
(b)
(c)
(d)
Q-15) A man waves his arms while walking. This is to
(a)
(b)
(c)
(d)
Q-16) Which of the following are examples of uniform velocity?
(a)
(b)
(c)
(d)
Uniform velocity:
Definition: The condition in which a body covers an equal level of distances in unequal intervals of time is called the uniform velocity.
Examples of uniform velocity
When a particle moves with a uniform velocity, the slope of a displacement-time graph (Fig) is constant at all points.
It is a stable velocity, i.e., the velocity that does not change with time in scale or direction in space. This means that a body has this type of velocity if it travels at a constant speed along an instant line (i.e., in an exacting direction). There has been no change in either speed or direction.
The following are some examples:
- The Moon’s orbit around the Earth
- The movement of a watch’s hands
- Earth’s Rotation Earth’s Revolution
- Raindrops fall on the Earth’s surface. This is the velocity with which a body moves once it is started on a frictionless surface.
- All circular motion is an example: the movement of a fan and our clock hand.
Q-17) Kepler’s second law (law of area) is nothing but a statement of
(a)
(b)
(c)
(d)
From Kepler's $2^{nd}$ law – The straight line joining the sun and the planet sweeps out equal areas in equal time intervals (${dA}/{dt}$ = const; area swept)
Areal velocity of the satellite is given by
${dA}/{dt}=1/2ωr^2 = const. = L/{2m}$
where ω = angular velocity of the satellite
L = mvr = mω$r^2$ = const, showing that Kepler's $2^nd$ law is a consequence of the conservation of angular momentum.
Q-18) The work done becomes zero if
(a)
(b)
(c)
(d)
Q-19) Rahul takes 1 minute to raise a box to a height of 1 metre and Rohan takes 1/2 minute to do so. Comment on the energy by the two.
(a)
(b)
(c)
(d)
Q-20) Frictional force
(a)
(b)
(c)
(d)
Friction always apposes relative motion between surfaces in contact and hence can act in any direction to oppose the relative motion.