Question Discussion & Solution

Detailed Video Concept and solution

Levers are classified into three types or class based on the position of load and effort on the fulcrum;

Class 1 Lever:

• A Class 1 lever has the fulcrum placed between the effort and load
• The movement of the load is in the opposite direction of the movement of the effort
• E.g. crowbars, scissors, pliers, tin snips and seesaws

Class 2 Lever

• A Class 2 lever has the load between the effort and the fulcrum
• In this type of lever, the movement of the load is in the same direction as that of the effort
• E.g. nutcrackers, wheelbarrows, doors, and bottle openers

Class 3 lever

• A Class 3 lever has the effort between the load and the fulcrum
• Both the effort and load are in the same direction
• E.g. tweezers, arm hammers, and shovels

The correct answer is Femur.

Key Points

• The largest bone in the human body is the femur, the thighbone.
• It is the largest, longest, and strongest bone in the human body.
• The femur runs from the keen to the hip.
• The Femur or thigh bone is the largest and heaviest bone in the human body.
• At the proximal end of the Femur, there is a rounded prominence which is called the Head of the Femur.
• The femur runs from the keen to the hip.
• It carries all the upper body weight.
• The other parts of the leg are the tibia, femur, fibula, and keep cap also known as patella.

Additional Information

• The human skeleton is made up of 206 bones, including bones of the
  • Skull:  including the jaw bone (mandible, maxilla)
  • Spine: cervical, thoracic and lumbar vertebrae, sacrum and tailbone (coccyx)
  • Chest: ribs and breastbone (sternum)
  • Arms: the shoulder blade (scapula), collar bone (clavicle), radius, humerus and ulna
  • Hands: wrist bones (carpals), metacarpals and phalanges
  • Pelvis: hip bones
  • Legs: the thigh bone (femur), the kneecap (patella), shin bone (tibia) and fibula
  • Feet: tarsals, metatarsals, and phalanges.

All are divisible by 10 except 25.

The correct answer is option 2 i.e 19.

• Potassium is a member of the alkali group of the periodic table.
  • Symbol: K.
  • Atomic number: 19.
  • Belongs to group 1 in the periodic table.
  • First isolated in 1807 by Humphry Davy.
  • Sodium and Potassium are the elements known as soft metals(can cut with a knife with little force).
  • Potassium metal is kept in kerosene due to its high reactivity with water.
  • Potassium bicarbonate is the chemical used in fire extinguishers.
  • Potassium is the most common radioisotope in the human body.
  • Potassium is the second least dense metal after lithium.
• Atomic Number 17: Chlorine.
• Atomic Number 18: Argon.
• Atomic Number 20: Calcium.

The correct answer is the Helium nucleus.

• Helium nucleus was the source of alpha particles in the Rutherford scattering experiment.
• Ernest Rutherford, a British scientist conducted an experiment and proposed the atomic structure of elements.

Key Points

• Rutherford conducted an experiment by bombarding a thin sheet of gold with α-particles.
• He then analysed the trajectory of these particles after their interaction with the gold foil.
• Since very few α-particles were deflected back, and only a few α-particles had nearly 180^o angle of deflection.
• Hence he concluded that the volume occupied by the positively charged particles in an atom is very small as compared to the total volume of an atom.