Inelastic collision problem

In summary, a bullet with a mass of 0.049kg and initial speed of 139m/s collides with a stationary block with a mass of 0.54kg, embedding itself in the block. The resulting velocity of the block and bullet is 11.5637 m/s and 0 m/s respectively. In order to determine the velocity, the system included both the bullet and the block. The assumptions made were that the gravitational force was negligible due to the short duration of the collision, and that the frictional force and upward force from the table were also negligible. However, it is important to note that these assumptions may not hold if the collision took place over a longer period of time.
  • #1
Westin
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Poster informed about mandatory use of homework template
A bullet is fired directly into a wood block (along the x-axis), which rests on a rough table. The bullet embeds itself in the block. (This is an inelastic collision: the block deforms and the block and bullet heat up as a result of the collision).

a) If the bullet has a mass 0.049kg and is initially moving with a speed of 139m[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmmi10/alpha/144/char3D.pngs, [Broken] while the block has a mass 0.54kg and is initially at rest, determine the velocity of the block and bullet just after the collision.

v[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmmi10/alpha/144/char7E.png=[PLAIN]https://s3.lite.msu.edu/adm/jsMath/fonts/cmex10/alpha/144/char1C.png [Broken] 11.5637 m/s , 0 m/s , 0 m/s https://s3.lite.msu.edu/adm/jsMath/fonts/cmex10/alpha/144/char1D.png

You are correct.
Your receipt no. is 147-6323

b) To determine the velocity of the bullet and block, what did you include in your system?
True: The bullet
True: The block
False: The table

You are correct.
Your receipt no. is 147-1738

c) Which of the following is true about your assumptions? (Be careful -- some are incorrect because the physics is incorrect!)

Select all that are True.
1)I neglected the gravitational force because the collision was short.
2)I neglected the gravitational force because it point in the negative y-direction and therefore doesn't affect the momentum in the x-direction.
3)I neglected the frictional force due to the table because the collision was short.
4)I neglected the upward force of the table force because it points in the y-direction and therefore doesn't affect the momentum in the x-direction.
5)I neglected the upward force of the table force because the collision was short.

Incorrect. Tries 2/3

I am confused with last question. To neglect a force since the collision was only .037s seems very iffy to me. Previous attempts were I said all were true, and #2, #4 were true. Both were wrong. My 3rd attempt is telling me #1 #3 #5 are true, what do you think?
 
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  • #2
I would think that you are only guessing at this point. For each alternative, try to argue why it is true or false and we might be able to help you clear up misunderstandings rather than just giving you the answers.
 

1. What is an inelastic collision?

An inelastic collision is a type of collision where the total kinetic energy of the colliding objects is not conserved. This means that after the collision, some of the kinetic energy is lost and converted into other forms of energy, such as heat or sound.

2. How is the momentum conserved in an inelastic collision?

In an inelastic collision, the total momentum is conserved. This means that the total momentum before the collision is equal to the total momentum after the collision. However, the individual momentums of the colliding objects may change.

3. What is the coefficient of restitution in an inelastic collision?

The coefficient of restitution is a measure of how much kinetic energy is lost during a collision. It is defined as the ratio of the relative velocity of the objects after the collision to the relative velocity before the collision.

4. How is an inelastic collision different from an elastic collision?

In an elastic collision, the total kinetic energy of the colliding objects is conserved. This means that the objects bounce off each other without any loss of kinetic energy. In contrast, in an inelastic collision, some of the kinetic energy is lost and the objects may stick together after the collision.

5. What are some real-life examples of inelastic collisions?

Examples of inelastic collisions include car crashes, billiard ball collisions, and dropping a clay ball onto a hard surface. In all of these examples, some of the kinetic energy is lost and converted into other forms of energy, such as sound or deformation of the objects.

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