Practice MCQ Questions and answers on Physics-GK

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.

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
−v² = u² + (−2gh)
400 = u² − 2x 10 x 25
u² = 900
=> u = 30 m/s

Any mass is attracted to the Earth by the pull of gravity. Gravity accelerates all objects towards the ground at a specific rate. Without any other forces present, the speed of an object in free fall will increase the farther or longer it falls. In general the air resistance on an object depends upon several variables. First, it depends upon the shape of the object. Its shape determines the object’s drag coefficient: the more aerodynamic the shape, the less drag. Second, it depends upon the size of the object; specifically the cross-sectional area presented to the airflow (perpendicular to the direction of travel). And lastly, it depends upon the speed of the object. At low speeds the object’s resistance is directly proportional to speed, and at higher speeds the object’s resistance is proportional to its speed squared. Most objects falling through the air would be considered to be moving at a higher speed, even though that speed might not be great compared to some velocities.

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.

When a particle is thrown vertically upwards in space, it will experience constant acceleration towards the ground (irrespective of the direction in which it is moving in), known as acceleration due to gravity. At the highest point, it has zero velocity but has downward acceleration equal to acceleration due to gravity.

Momentum is conserved in all types of collision whether it is elastic or inelastic where as kinetic energy is lost in sound energy in the absence of external force in inelastic collision.

The dimensions of Force are M (mass), L (length) and T^-2(time). It can also be expressed as [newton] = [kilogram] [metre] [second]^-2.

If lift is going up with acceleration, the apparent weight of a body is more than the true weight.

The force that generates wind is pressure gradient force.

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.