A cameraman sitting near the open door of a news helicopter accidentally drops his 140-g mobile phone out
the door at an altitude of 990 m. How fast will the phone be falling when it strikes the ground?
A. 9.8 m/s
B. 140 m/s
C. 850 m/s
D. 990 m/s

140m/s

Explanation:

Given parameters:

Mass of mobile phone  = 140g

Altitude  = 990m

Unknown:

Final velocity   = ?

Solution:

This is a motion problem. It is solvable by using the right motion equation. For this problem, understand that the phone is dropping under the influence of gravity.

      V²   =  U²  +  2gH

where V is the final velocity

           U is the initial velocity

           g is the acceleration due to gravity

          H is the height of fall

Initial velocity is 0

Input the variables;

      V²   = 0²   +  2(9.8)(990)

       V  = 139.29m/s = 140m/s

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2