Physics - Study Mode

[#261] Materials for rain-proof coats and tents owe their water-proof properties to
Correct Answer

(A) surface tension

Explanation

Solution: The material of rain proof coats have the property of not minimizing the surface tension which will tend the water molecule to be in its drop form.

[#262] RADAR is used for:
Correct Answer

(D) detecting and locating the position of objects such as Aeroplanes.

Explanation

Solution: RADAR is used for detecting and locating the position of objects such as Aeroplanes.

[#263] If an electron and a photon have the same wavelength, then they will have the same
Correct Answer

(B) Linear momentum

Explanation

Solution: When a non-relativistic electron and a non-relativistic proton are moving and have the same de Broglie wavelength, then they will have the same linear momentum p = mv. If the electron and proton have the same momentum, they cannot have the same speed because of the difference in their masses. An electron and photon can have the same wavelength since the wavelength of electron can be changed by changing its velocity.

[#264] A ball is thrown vertically upward from the ground. It crosses a point at the height of 25 m twice at an interval of 4 seconds. The ball was thrown with the velocity of
Correct Answer

(C) 30 m/s

Explanation

Solution: The interval between object pass the same point is 4 sec. That means in 2 sec, object reaches the top and in next 2 sec, it again reaches the same point. By the info given, we can find the velocity of that point by using : v=u+(-gt) 0= u - 10×2 u = 20 Then the velocity at 25m is 20m/sec. so the initial velocity is −v 2 = u 2 + (−2gh) 400 = u 2 − 2x 10 x 25 u 2 = 900 => u = 30 m/s

[#265] A particle dropped from the top of a tower uniformly falls on ground at a distance which is equal to the height of tower. Which of the following paths will be traversed by the particle ?
Correct Answer

(B) Parabolic

Explanation

Solution: If a particle dropped from the top of a tower uniformly falls on ground at a distance which is equal to the height of tower then a parabolic path will be traversed by a particle because when the particle is dropped that point is called the point of projection and when it reaches the ground that point is called the point of impact. Now, if the two points is met with one another the curve emerges is parabolic in nature. Hence, we can say that the path followed by the particle is of parabolic trajectories.