Physics MCQs

Notes:
Alpha radiation is not used in radiotherapy because it cannot penetrate human skin. Alpha particles are a highly ionizing form of particle radiation with a short range. They can be stopped by a few centimeters of air or by skin. This means that external therapy would be useless because the alpha radiation would not be able to enter the body.  Alpha particles have a very large atomic volume. They are given additional mass by the two neutrons they contain. This facilitates ionization by coulombic interaction or direct collision of the alpha particle with atomic electrons.  Radiation therapy is a treatment that uses ionizing radiation to kill or control the growth of malignant cells. It is often delivered by a linear particle accelerator.

Notes:
When we press the top of bottle the pressure at top of the bottle decreases and hence, the velocity of liquid flow increases. Bernoulli’s Principle states that an increase in the speed of a fluid produces a decrease in pressure and that a decrease in the speed of a fluid produces an increase in pressure. The principle states that the total energy of a moving fluid remains constant at all times.

Notes:
Werner Heisenberg, a german Physicist, discovered the Uncertainity principle. As per the uncertainty principle, we cannot measure the position (x) and the momentum (p) of a particle with absolute precision. The more accurately we know one of these values, the less accurately we know the other. It represnts the effects of wave-particle duality on the properties of subatomic objects.

Notes:
The unit of Velocity Gradient is s^-1(per second) Velocity Gradient = Velocity/time Velocity gradient shows that how the velocity of a fluid changes between different points within the fluid.

Notes:
The curie is a unit of ionizing radiation (radioactivity). It is symbolized with Ci . 1 curie = 3.7 x 10 10 disintegrations or nuclear transformations per second. This is approximately the amount of radioactivity emitted by one gram (1 g) of radium-226. The unit is named after Pierre Curie, a French physicist.

Notes:
The branch of mechanics which deals with the study of motion of material objects without taking into account the factors which cause motion is called as Kinematics. The branch of mechanics which deals with the study of motion of material objects taking into account the factors which cause motion is called as Dynamics. The branch of mechanics which deals with the study of material objects at rest is called as Statics.

Notes:
Electron volt is a practical unit of energy. Some practical units of energy are: 1 erg = 10^-7 J 1 calorie = 4.2 J 1 Kilowatt hour = 3.6 x 10⁶ J 1 Electron volt(ev) = 1.6 x 10^-19 J

Notes:
Potential energy is stored in the spring of a watch. Potential energy is the energy by virtue of an object’s position relative to other objects. It is often associated with restoring forces such as a spring or the force of gravity.

Notes:
If the rate of rotation of earth increases then the value of acceleration due to gravity decreases at all the places on the surface of earth except at poles.

Notes:
The value of escape velocity is different for different planets. For earth, this value is 11.2 km s^-2.