# Basic Momentum and Energy

#### Ronaldo21

Basic Momentum and Energy!!!!

1. (part 1 of 2) A 4.78 g bullet moving at 510.8 m/s penetrates a tree trunk to a depth of 4.93 cm. a) Use work and energy considerations to find the magnitude of the force that stops the bullet.

for this i did 1/2mv^2=w=fd
so 1/2(.00536)(681.8)^2=w=fd
1245.801323=fd
1245.801323=f(.0379)
and i solved for f and got 32870.74731

2. (part 2 of 2) b) Assuming that the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment the bullets stops moving.

for this one i just did vf^2=vi^2+2at. is that correct??

THANK YOU!!

#### Stonebridge

Re: Basic Momentum and Energy!!!!

The numbers in your solution to part one are not those in the question!

### The Physics Forums Way

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving