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Q:

# A boy sitting in a train moving with a uniform velocity drops a coin outside. A man standing outside the train will find the trajectory of the coin to be

 A) a parabola B) a horizontal straight line C) a vertical straight line D) a circle

Answer:   A) a parabola

Explanation:

Parabola, because when the coin is dropped at a particular point, it has the same velocity as the running train. So, by Newton's first law, it continues its motion horizontally with that velocity. But then, it is also pulled down by earth's gravity continuously. In this situation its horizontal motion gives way to the parabolic motion until it reaches the ground.

Subject: Physics
Q:

What is the full form of "RADAR" ?

 A) Radio Detecting and Ranging B) Region Device and Ranging C) Radio Detect and Rangs D) Radio Device and Ranging

Explanation:

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6 180
Q:

If a carrier wave of 1000 kHz is used to carry the signal, the length of transmitting antenna will be equal to _____ ?

 A) 300 m B) 30 m C) 3 m D) 0.3 m

Answer & Explanation Answer: A) 300 m

Explanation:

h =   = 3 × 108/106 = 300 m

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5 247
Q:

Quality of transmission depends upon

 A) Nature of signal only B) Nature of medium only C) Both (A) and (B) D) Neither A nor B

Answer & Explanation Answer: C) Both (A) and (B)

Explanation:

Quality of transmission is governed both by nature of signal and nature of communication channel/medium.

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5 238
Q:

The rate of change of linear momentum of a body falling freely under gravity is equal to it's ____ ?

 A) Kinetic Energy B) Weight C) Potential Energy D) Impulse

Explanation:

Rate of change of impulse equals the force . In case of freely falling body the only force is the weight.

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5 326
Q:

A disk and a sphere of same radius but different masses roll on two inclined planes of the same altitude and length. Which one of the two objects gets to the bottom of the plane first ?

 A) Depends on their masses B) Sphere C) Disk D) Both reach at the same time

Explanation:

Time does not depend on mass, else

$\inline \fn_jvn T \prec \sqrt{\left ( 1 +\frac{k^{2}}{R^{2}} \right )}$

$\inline \fn_jvn \frac{k^{2}}{R^{2}}$  => is least for 'sphere' and

hence least time is taken by sphere.