# Finding the force during impact

1. Oct 25, 2013

### koii123

1. The problem statement, all variables and given/known data
An inspector performed a drop test:
He released a plastic electronic product (2kg) at the height 1.3m from the ground. The plastic product than hit the ground, and bounced 0.1m after impact. Time of contact =0.1s

Find the maximum force acting on the object during impact. Assume the ground is perfectly elastic.

2. Relevant equations
Potential energy = mgh
Work done = Fd

Then, Force acting on the object = F = mgh/d

3. The attempt at a solution
F=2(9.8)1.3/0.1

Is this correct??

Last edited: Oct 25, 2013
2. Oct 25, 2013

### Staff: Mentor

It doesn't seem like there's nearly enough information given to calculate the maximum contact force during impact. In fact, even if you wanted to determine the average force during impact, you would still need to know the contact time.

Chet

3. Oct 25, 2013

### koii123

actually, suppose there is enough information, how to calculate?
and how to use the contact time?

4. Oct 25, 2013

### nil1996

we cant assume the time of contact to be something. It should be noted in the problem.

5. Oct 25, 2013

### koii123

i have updated the time of contact: 0.1s,
so how to calculate it?

6. Oct 25, 2013

### nil1996

wait if you want the impulse then you can just find the change in momentum without the need of the time period.

7. Oct 25, 2013

### nil1996

remember that it is said that ground is perfectly elastic but not the plastic box.
Using work energy theorem you can find the velocities before and after collision.

Last edited: Oct 25, 2013
8. Oct 26, 2013

### Tanya Sharma

koii123... First calculate the velocity of the object just before it touches the ground ? You can use either energy conservation or kinematics equation .

Last edited: Oct 26, 2013