Question

An elevator is descending with uniform acceleration. To measure the acceleration, a person in the elevator drops a coin at the moment the elevator starts. The coin is 6 ft above the floor of the elevator at the time it is dropped. The person observes that the coin strikes the floor in 1 sec. Calculate from these data the acceleration of the elevator?

Answer 1

Answer:

For elevator and coin : Initial velocity=u=0m/s

As the elevator descends with uniform acceleration "a" the coin has to move more distance than 1.8cm to strike floor.

time taken =t=1 sec

Scoin=Sc=ut+1/2at²

Sc= 0+1/2at²

=1/2 xg x1²

Sc=g/2

Se=ut+1/2 at²

=0+1/2 a(1)²

Se=a/2

Total distance travelled by coin is given by :

1.8 +1/2 a =1/2g

1.8 +a/2 =g/2

1.8+a/2=9.8/2

a/2=4.9 -1.8=3.1m

a=6.2 m/s2

a= 6.2 x 3.28 = 20.34 ft/s²