Calculation of Weight When Velocity Is Uniform

Calculation of Weight When Velocity Is Uniform

According to Newton’s Law of Motion, no force is required to keep a body moving with uniform velocity in a straight line. The air inside the Lift moves with the body, so the question of air resistance does not arise. Gravity pulls the body down with a force of mg. The body presses on the lift floor with the same force. By Newton’s Third Law of Motion the floor exerts an equal upward reaction on the body. Consequently the resultant force on the body is zero and it is the requirement of uniform velocity in any direction. Hence when the lift is moving upward with uniform velocity, the weight of the body is mg, the same as when rest on earth.