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# 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 circle C) a horizontal straight line D) a vertical straight line

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

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• Related Questions

On the Kelvin scale ,the melting point of ice is

 A) 373K B) 100K C) 273K D) 0 K

Explanation:

Subject: Physics

1

Water has maximum density at............

 A) 0 C B) -15 C C) 4 C D) 15 C

Answer & Explanation Answer: C) 4 C

Explanation:

Subject: Physics

0

Fish and other aquatic creatures canlive inside a deep frozen pond because

 A) fish are cold-blooded animals B) ice is a bad conductor of heat C) there will always be water just beneath the ice level D) they can adapt themselves to live in ice

Answer & Explanation Answer: C) there will always be water just beneath the ice level

Explanation:

Water has maximum density at $\inline \fn_jvn 4^{0}C$. So at this temperature it sinks down to bottom and stays here. If it cools further, it will become less dense and move up. So while the upper layers can cool enough to form ice, the bottom layers remain as water at $\inline \fn_jvn 4^{0}C$$\inline \fn_jvn \therefore$ (C) is correct.

Subject: Physics

11

At what temperature do the Fahrenheit and celcius scales give the same reading?

 A) 212 degrees B) 32 degreees C) -40 degreees D) 0 degreees

Answer & Explanation Answer: C) -40 degreees

Explanation:

$\inline \fn_jvn F=C\times \frac{9}{5}+32$ We want the temperaature when F=C. So substituting C For F, we have C = $\inline \fn_jvn F=C\times \frac{9}{5}+32$

$\inline \fn_jvn \therefore$ C = -40. Thus when C = -40, we have C = F i.e, $\inline \fn_jvn -40^{0}F$

$\inline \fn_jvn \therefore$ (C) is coorrect. i.e,$\inline \fn_jvn -40^{0}C=-40^{0}F$

Subject: Physics

12

Pieces of camphor placed on water move about rapidly. This is because of

 A) diffusion B) viscosity C) surface tension D) capillarity

Answer & Explanation Answer: C) surface tension

Explanation:

The Camphor slowly dissolves in the water lowering the latter's surface tension in the immediate neighbourhood. The stronger pull exerted by the uncontaminated portion of water brings about a movement of the surface and the camphor particles are carried along with it. When after sometime the whole surface settles for the reduced tension, the movement of the camphor too short.