• SLC Science
  • Gravitational force
    • Law of gravitation
    • Acceleration(g)
    • Free fall
    • Numerical Problems
  • Pressure
    • Def.Pressure
    • Principles
    • Upthrust
    • Numerical Problems
  • Heat
    • Heat Energy
    • Anomalous expansion of water
    • Specific heat capacity
    • Numerical Problems
  • Electricity
    • Electricity
    • Fuse
    • Faraday'sPrinciple
    • Transformer
    • Numerical Problems
• SLC English
• SLC Mathematics
• SLC Opt.Maths
• +2 Science
  • Wave Motion

Free fall
Definition:

• Without any kind of resistance falling object is called free fall.
• Under free fall each object fall under the action of gravity only.
• In this situation all falling objects have equal falling acceleration and equal to gravitatonal acceleration of that place.
• Under free fall all objects (feather and coin, wrapped paper and unwrapped paper) fall together and reache at same time to the ground.
• All object on moon(no air) fall freely and reached to surface together.
• Fall of parachute on earth surface is not free fall but fall of parachute on moon is free fall

Q. Fall of stone on earth surface is considered to be free fall but fall of parachute is not free fall, why ?
→ On stone air resistance is negligible so it is considered free fall but air resistance on parachute is countable so it is not free fall.
Q. What is the difference between fall of parachute on Earth surface and on moon surface ?

→
• On earth surface there is excessive upward air resistance on parachute so it is not free fall and fall swoly so it is possible to jump from aeroplane or hill
• on moon surface there no air resistance so it is free fall.

Q. Is the gravitational acceleration is zero during free fall?
→ No, it is not zero. During free fall objects have acceleration equal to gravitational acceleration of that place.
Weightlessness Definition:

• During free falf, falling object seems to weightless, is called weightlessness.
• Actually free falling objects are not weightless it is only seems to us.

Q. Can the condition of weightlessness be called masslessness?
→ No, its don't called masslessness. Because during weightlessness objects seems weightless only but actually its weight (pulling force) and mass of object remain.
Q. Mentiona any two difference between weightlessness due to freefall and weightlessness in space?

• Weightlessness due to free fall : During freefall both object as well as measuring instruement(spring balance) fall with acceleration equal to 'g' so spring balance couldn't show weight. Therefor object seems weightlessness.This is our inability to measure weight of free falling object.
• Weightlessness in space : In space acceleration due to gravity is zero (i.e. g=0) therefor weight of the object seems to zero. (w=mg=m.0=0). This is because of no (negligible) gravitational force in space

Do yourself

• Q. Write down the value and SI unit of gravitational constant.
• What is the value of acceleration due to gravity at the center of earth? Why do tides rise in the sea?
• Prove that: F= G m₁m₂ / d²
• Calculate the change in gravitational force between two bodies when the distance between them is made double; keeping their mass constant.
• What is the relation of force of gravitation with masses of the objects and distance.
• What is meant by the statement that the acceleration due to gravity on the surface of the moon is 1.67 msec^-2?
• Prove that: g ∝ 1 / R²
• What is the direction of aaceleration due to gravity? Give reason also.
• What is the relation between the weight of an object and the radius of the earth?
• When will an object inside the gravitational field of the earth be weightless?
• It is difficult to lift a larger stone on the surface of the earth but easy to lift smaller one why?
• What is the magnitude of acceleration due to gravity in the space? Why? Give reason regarding the fact that parachutists are not hurt when they jump out of an airplane.
• If Kathmandu lies in high altitude than Biratnagar from sea leve, then where an object does has more weight among two places? Give reason.