Practice MCQ Questions and answers on Physics-GK

The ballpoint pen is one of the most simple and yet ubiquitous devices whose function depends on surface tension. With a pen held upright, gravity and surface tension act in concert to get ink onto the ball.

When detergent is added to water, it decreases the surface tension of the water. Compounds that lower water's surface tension are called surfactants, which work by separating the water molecules from one another.

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.

The SI unit of dynamic viscosity is the newton-second per square meter.

When the brush is taken out of water, the hairs cling together due to surface tension. This happens because the free surface of water tries to acquire a minimum surface area.

When an object falls through a fluid, it attains a constant velocity through its subsequent motion. This happens because the net force on the body due to gravity and fluid becomes zero. This constant velocity is termed as terminal velocity.

An orbiting satellite is a projectile in the sense that the only force acting upon an orbiting satellite is the force of gravity. A satellite is acted upon by the force of gravity and this force does accelerate it towards the Earth. In the absence of gravity a satellite would move in a straight line path tangent to the Earth. In the absence of any forces whatsoever, an object in motion (such as a satellite) would continue in motion with the same speed and in the same direction. The force of gravity acts upon a high speed satellite to deviate its trajectory from a straight-line inertial path. Indeed, a satellite is accelerating towards the Earth due to the force of gravity. As far as spoon dropped by astronaut in a satellite is concerned, it continues to follow the motion of the satellite as there is inertia of motion acting upon it.

It happens because of gravity. A key feature of super maneuvering aircrafts is a high thrust-to-weight ratio; that is, the comparison of the force produced by the engines to the aircraft’s weight, which is the force of gravity on the aircraft. A thrust-to-weight ratio greater than 1:1 is a critical threshold, as it allows the aircraft to maintain and even gain velocity in a nose-up attitude; such a climb is based on sheer engine power, without any lift provided by the wings to counter gravity, and has become crucial to aerobatic maneuvers in the vertical loop.

Law of speed is not a part of Kepler's Law.

The square of the time period of the planet is directly proportional to the cube of the semimajor axis of its orbit.