*Fnet is referred to as the impulse for which the symbol J is used. the equation fnet=mv is often referred to as the impulse momentum theorem in many text books.

*Internal forces do not affect the momentums system, because of Newtons third law, the forces acting between masses within a system cancel in pairs and do not contribute to the systems momentum.

*Momentum can be conceived in one direction but not in another.

P is momentum, M is mass, and V is velocity

terms

• gravitational force (Fg)

• Gravitational field (g

  Fg=G m1/m2 r^2. Symbol breakdown: Fg is gravitational force, G is the gravitational force, g is the gravitational constant, m1 and m2 are point masses, and r is the distance

  Meaning: the gravitational between masses m1 and m2 is directly proportional to their masses and inversely proportional the the square of the distance between them.

  g=Fg/m2+Gm1/r2>. Symbol breakdown: g is the gravitational field strength.

  Meaning: the gravitational field strength is directly proportional to mass creating the field and inversely proportional to the square of the distance

• Fg is the gravitational force between M1 and M2

• G is the gravitational constant equal to 6.67x 10-11 m3/kg.S2

• g= gravitational force per unit mass

• We can find the strength of a gravitational field of mass M1 on any object with mass M2 by dividing the above equation by M2 and simplifying

• The variable r is the distance between the centers of mass

Newtons law of Motion

• newton’s __firs__t law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an extreme force.

• Newton’s second law states that the rate of a change of momentum of a body is directly proportional to the force applied and this change in momentum takes place in the direction of the applied force

• Newton’s third law states that for every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other were always equal, and directed to contrary.

Nucleus

• the proton-electron hypothesis proposed that the nucleus constitutes protons and electrons.

• the proton-neutron hypothesis proposed that nuclei might be composed of protons and neutrons, collectively called nucleons.

• the number of protons, the Atomic Number, in the nucleus is represented with the letter A.

• the mass number is the total number of protons and neutrons present in the nucleus represented with the letter Z.

• Neutron number, the total number of neutrons in the nucleus, is equal to A-Z, represented with the letter N.

• different nuclear models have been developed to understand the structures and properties of the nucleus.

• the emission of a-particles is assumed by the combination of 4 protons and 2 electrons in the nucleus

• both protons and neutrons have quantum number ½.

Nuclear Physics

• Particles can interacr with the nucleus or can be captured by the nucleus and cause nuclear reactions

• Fission reactions take place when have nuclei capture incident particle

• Fusion Reactions take place when two light nuclei combine to form a heavier nucleus

• there are three types of radiation: alpha, Beta and Gamma decay

• the activity of a radioactive nuclide is defined as the number of disintegration per unit of time

• half - life is the time required for the number of radioactive nuclides to reduce to half by disintegration.

Resolution of a vector

Then, we have

P = OA = OB + BA

But since OB is parallel to p, and BA is parallel to q, we can write:

OB = m p, and

BA = n q

where m and n are real numbers.

Therefore,

P = m p + n q

Now P is said to be resolved into two component vectors m p and n q along with p and q respectively.

A vector P in the x - y plane can be resolved into its components along the X direction and Y direction as shown in figure c.

P = P_xi + P_yj

Consider a vector V. The component along the horizontal direction X- axis is, V_x cosθ and in the vertical direction Y axis is, V_ysinθ.

When an object is placed on an inclined plane, the weight acts in two dimensions. The weight vector may be represented in terms of parallel and perpendicular components F_gx and F_gy.

(b) By resolution of forces

The weight F_g acting vertically downwards may be resolved into its components. F_gsinθ acting parallel to and down the plane and F_gcosθ acting perpendicular to the plane.

more on forces

• Normal force/Normal reaction - A body placed on a surface exerts a force on the surface. The surface also exerts a force on the body. The force exerted by the surface on the body is known as the normal reaction (force) and is represented by N. It is always perpendicular to the surface at the point of contact.

• Frictional force - When a body tends to move on a surface its motion is resisted by a force acting in opposite direction. This resistive force from the contact to the surface and is known as frictional force.

• Tension - When a cord or a rope is attached to a body and pulled, the cord exerts a force T directed away from the body towards the cord. This pulling force is known as tension.