physics
posted by ARS .
a lift is moving downward with uniform acceleration to measure the acceleration a person in the lift drops a coin 6 ft above the floor of the lift . the coin strikes the floor in 1 second find the acceleration

The "effective" acceleration rate, a' , (measured positive downward) as observed in the elevator
satifies the equation
6 = (1/2)a' t^2 = a'/2
since t = 1 second to fall 6 feet)
Therefore a' = 12 ft/s^2
Without elevator acceleration, the observed downward acceleration rate would be g = 32.2 ft/s^2
Since a' = g a,
where a is the true acceleration rate (downward),
a = 32.2  12 = 20.2 ft/s^2