# Homework Help: Velocity of a falling object

1. Aug 7, 2012

### Physics-Pure

1. The problem statement, all variables and given/known data

A ball of mass 0.163 kg is dropped from a
height 1.89 m above the ground.
The acceleration of gravity is 9.8 m/s^2
Neglecting air resistance, determine the
speed of the ball when it is at a height 0.997 m
above the ground.
2. Relevant equations

Gravitational Energy = Kinetic Energy

Mass x Acceleration From Gravity x Height = 1/2 (mass)x(velocity)^2

Acceleration From Gravity x Height = 1/2 (velocity)^2 [mass cancels]

3. The attempt at a solution

(9.8 m/s^2) x (1.89m) = 1/2 (velocity)^2

Velocity^2 = 2[(9.8 m/s^2) x (1.89m)]

Velocity = ~6.08 m/s
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Aug 7, 2012

### voko

This is correct only when one kind of energy is converted entirely into another. Which is not the case in this problem. What equation should you really use?

3. Aug 7, 2012

### Physics-Pure

Vf = sqrt 2a delta y?

4. Aug 7, 2012

### azizlwl

Check the height.