A body, starting from rest, falls from a building and reaches the ground in 2 secs. What will be the velocity of the body when it reaches the ground? (Acceleration due to gravity = 10 ms^-2 ) 

The correct answer is 20 m/s.

Key Points

• The body starts from rest, so the initial velocity (u) is 0 m/s.
• The time (t) taken to reach the ground is 2 seconds.
• The acceleration due to gravity (g) is 10 m/s².
• The final velocity (v) can be calculated using the formula v = u + gt.
• Substituting the values, v = 0 + (10 m/s² * 2 s) = 20 m/s.

Additional Information

• Acceleration due to Gravity (g):
  • It is the acceleration that the Earth imparts to objects due to gravity.
  • The standard value of g on Earth's surface is approximately 9.8 m/s², often rounded to 10 m/s² for simplicity in calculations.
• Free Fall:
  • It is the motion of a body where gravity is the only force acting upon it.
  • In a vacuum, all objects fall at the same rate regardless of their masses.
• Equations of Motion:
  • These equations describe the relationship between displacement, velocity, acceleration, and time.
  • Commonly used equations include: v = u + at, s = ut + 0.5at², and v² = u² + 2as.
• Terminal Velocity:
  • It is the constant speed that a freely falling object eventually reaches when the resistance of the medium prevents further acceleration.
  • For objects falling through air, terminal velocity depends on the object's size, shape, and mass.