 General Knowledge Quiz for CDS 2020(Newton's Laws and Circular Motion): 2nd Jan 2020

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Q1. Who among the following anticipated Newton by declaring that all things gravitate to the earth?

(a) Aryabhatta
(b) Varahamihira
(c) Buddhagupta
(d) Brahmagupta

Q2. What is the working principle of a washing machine?

(a) centrifugation
(b) dialysis
(c) reverse osmosis
(d) diffusion

Q3. A ball is dropped from the top of a high building with a constant acceleration of 9.8 m/s2. What will be its velocity after 2 seconds?

(a) 9.8 m/s
(b) 19.6 m/s
(c) 29.4 m/s
(d) 39.2 m/s

Q4. Assertion (A) : A man standing on a completely frictionless surface can propel himself by whistling.
Reason (R) : If no external force acts on a system, its momentum cannot change.

Codes:
(a) Both A and R are true and R is the correct explanation of A
(b) Both A and R are true but R is not a correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

Q5. The mass of a body on earth is 100 kg (acceleration due to gravity, g= 10 m/s2). If acceleration due to gravity on the moon is g/6, then the mass of the body on the moon is

(a) 100/6 kg
(b) 60 kg
(c) 100 kg
(d) 600 kg

Q6. If the radius of the earth were to shrink by one percent, its mass remaining the same, the value of g on
the earth’s surface would __________.

(a) increase by 0.5%
(b) increase by 2%
(c) decrease by 0.5%
(d) decrease by 2%

Q7. A car is running on a road at a uniform speed of 60 km/h. The net resultant force on the car is ?

(a) driving force in the direction of car’s motion
(b) resistance force opposite to the direction of car’s motion
(c) an inclined force
(d) equal to zero

Q8. A spherical body moves with a uniform angular velocity (w) around a circular path of radius r. Which one of the following statements is correct?

(a) The body has no acceleration
(b) The body has a radial acceleration w2r directed toward centre of path
(c) The body has a radial acceleration 2/5w2r directed away from the centre of the path
(d) The body has an acceleration w2 tangential to its path

Q9. Which among the following terms describes the natural tendency of an object to remain at rest or in motion at constant speed?

(a) Inertia
(b) Momentum
(c) Equilibrium
(d) Acceleration

Q10. A body whose momentum is constant, must have constant __________.

(a) Weight
(b) Acceleration
(c) Velocity
(d) Force

Solutions

S1. Ans.(d)
Sol. Brahmagupta was an Indian mathematician and astronomer. He anticipated Newton by declaring that all things gravitate to the earth.

S2. Ans.(a)
Sol. Centrifugation is a process that involves the use of the centrifugal force for the separation of mixtures with a centrifuge.

S3. Ans.(b)
Sol. The velocity after time t is given by
v = u + gt
Here, u = 0, t = 2s, g = 9.8 m/s2
v = 0 + (9.8 × 2) = 19.6 m/s

S4. Ans.(b)
Sol. First statement involves the use of Newton's third law of motion, "For every action there is an equal and opposite reaction". In first case while whistling a man uses his breathe as a propellant to propel himself. The second statement can be explained on the basis of law of conservation of linear momentum according to which the momentum of body remains conserved until any external force acts upon it.

S5. Ans.(c)
Sol. Mass is a universal constant. The mass of a body remains unchanged.

S6. Ans.(b)
Sol. The value of g on earth's surface is given by g=GM/R2.
Thus, if radius of the earth shrinks by 1%, the value of g will increase by 2%.

S7. Ans.(d)
Sol. By Newton's second law F = ma. If a = 0, Fnet = 0. Thus, the resultant force is zero.

S8. Ans.(b)
Sol. A body moving with a uniform angular velocity(w) on a circular path of radius r has radial acceleration equal w2r directed towards the centre of the path.

S9. Ans.(a)
Sol. Inertia is a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force.

S10. Ans.(c)
Sol. Momentum is defined as the quantity of motion of a moving body, measured as a product of its mass and velocity.  