Question

what is the speed of a 2.5-kilogram mass after ot has fallen freely from rest through a distance of 12 meters? a) 4.8 m/s b) 15 m/s c) 30. m/s d) 43 m/s

Answer 1

Vf^2 = Vi^2 + 2ad
Vf^ = 0 + 2(-9.8)(-12)
Vf^2 = 235.2
Vf = 15.3 m/s 

The correct answer is b) 15 m/s 

Answer 2

v₀ = initial velocity of the mass = 0 m/s                (since the mass falls from rest)

a = acceleration = acceleration due to gravity = 9.8 m/s²

d = vertical distance traveled = 12 m

v = final velocity of the mass

Using the kinematics equation

v² = v₀² + 2 a d

v² = 0² + 2 (9.8) (12)

v² = 235.2

v = √235.2

v = 15 m/s

hence the speed of mass comes out to be

b) 15 m/s