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:
A projectile will achieve maximum horizontal range when it is projected at an angle of 45°. This concept of maximum horizontal range is used by athletes in long jump, javelin throw, cricket ball throw etc

Notes:
Force can be defined as an external effort in the form of push or pull which: (i) Produces or tries to produce motion in a resting body (ii) Stops or tries to stop a moving body (iii) Changes or tries to change the direction of motion of the body

Notes:
Joule is the absolute unit of work in S.I 1 joule = 1 Nm

• 1 joule= 10⁷ ergs (erg is the unit of work in c.g.s)
• 1 erg = 1 dyne cm
• Also, Kilogram-metre (kg-m) is the gravitational unit of work on S.I 1 kg-m = 9.8 j

Notes:
For a given planet, greater the radius of orbit, lesser will be the orbital velocity of the satellite. The Orbital velocity depends on the mass of central body and radius of orbit.

Notes:
Force constant of material of wire is the force required to produce unit elongation in a wire. It is denoted by k. K = F/l or K = YA/l

Notes:
The forces between the atoms because of the electrostatic interaction between the charges of the atoms are called interatomic forces. These forces are active if the distance between the two atoms is of the order of atomic size i.e. 10^–10 metre. These forces are electrical in nature.

Notes:
The pressure is defined as the normal force acting per unit area. It is denoted by P. P = Force/Area It is the physical force exerted on an object and the force applied is perpendicular to the surface of objects per unit area.

Notes:
The potential energy of surface molecules per unit area of the surface is called as surface energy. Some work is required to be done, in bringing a molecule from the interior of the liquid to the free surface, against the intermolecular force of attraction. This work which is stored as potential energy of the molecule on the surface.

Notes:
The SI unit of viscosity is poiseiulle (Pl). Its other units are N s m^-2 or Pa s.