# Acceleration Question

1. Oct 7, 2004

### Squiller

In science we had to build a device which, when dropped 3 stories onto cement, should not allow an egg inside inside of it to crack. One of the follow up questions says : Why should your device accelerate slightly slower than the gravitational acceleration of 9.8 m/s/s " - I cant understand why this would be ? Please help

2. Oct 7, 2004

### Sirus

What other force is acting on an object falling through the air?

3. Oct 7, 2004

### Squiller

other forces are the air resistance and the gravitational pull, but why would an object travel less then 9.8 m/s/s if its in freefall ?

4. Oct 7, 2004

### Pyrrhus

Do the forces analysis

Using newton's 2nd law

$$\sum_{i=1}^{n} \vec{F}_{i} = m \vec{a}$$

We get (where R is air drag the resistive force)

$$m \vec{g} + \vec{R} = m \vec{a}$$

5. Oct 7, 2004

### Diane_

Remember, too - if the object is experiencing air resistance, it isn't truly in free fall.