Essential Science Concepts and Physics Calculations

Definition of Average Speed

The average speed of a body is the total distance traveled divided by the total time taken to cover this distance.

Electron Shells in Sodium Ion (Na+)

Na+ is a positively charged sodium ion. Normally, an atom of sodium has 11 electrons; according to the formula, it has 2 electrons in the K shell, 8 electrons in the L shell, and 1 electron in the M shell. However, Na+ has only 10 electrons; therefore, it has 2 electrons in the K shell and 8 in the L shell. Since 2 and 8 are the full capacities of the K and L shells respectively, Na+ has completely filled K and L shells.

Safety Measures in High Jump Events

In a high jump athletic event, athletes are made to fall on either a cushioned bed or a sand bed. If the athlete were to fall on a hard surface like a cement floor, their momentum would be reduced to zero in a very short amount of time. This increases the rate of change of momentum, causing a large opposing force to act on the athlete, which can lead to serious injury.

Understanding Valency: Silicon and Oxygen

Valency is the combining capacity of an atom.

• In the case of silicon, it has 4 electrons in the outermost shell; thus, it is deficient by 4 electrons to have a fully filled outermost shell. Hence, its valency is 4.
• In the case of oxygen, it has 6 electrons in the outermost shell; thus, it is deficient by 2 electrons to have a fully filled outermost shell. Hence, its valency is 2.

Local Immunization Programmes

The following immunization programmes are available at health centers:

1. Immunization for infants: DPT, BCG, Polio, Measles, and MMR.
2. For children: Typhoid, TT, DT, Smallpox, and TAB.

Diseases like typhoid and polio are major health problems in our locality.

Functions of Plastids

The chloroplasts are probably the most well-known of the plastids. These are responsible for photosynthesis. The chloroplast is filled with thylakoids, which is where photosynthesis occurs, and chlorophyll.

Calculating Velocity on an Inclined Plane

A trolley, while going down an inclined plane, has an acceleration of 2 cm/s². What will be its velocity after 3 seconds of start?

Given:

• Initial velocity (u) = 0
• Acceleration (a) = 2 cm/s²
• Time (t) = 3 s
• Final velocity (v) = ?

Calculation:
v = u + at
v = 0 + (2 × 3)
v = 6 cm/s

The final velocity is 6 cm/s.