Wooden block Momentum problem

In summary, a 2.0-kg block of wood is shot 25 cm above a tabletop by a 7.0-g bullet that lodges in the block. To find the initial velocity of the bullet, you can use the equation s=vi(t)+1/2(a)(t)^2 and eliminate the time variable by using the fact that the block travels 25 cm in the vertical direction. Alternatively, you can use the principle of energy conservation.
  • #1
creynaud
4
0

Homework Statement


A 2.0-kg block of wood rests on a tabletop. A 7.0-g bullet is shot straight up through a hole in the table beneath the block. The bullet lodges in the block, and the block flies 25 cm above the tabletop. How fast was the bullet going initially?

Homework Equations


initial m_bullet(initial v_bullet)+initial m_wood(initial v_wood)=(m_bullet+m_wood)Final v

The Attempt at a Solution


I know I am looking for the initial velocity of the bullet but how do I get the final velocity of the block of wood once it was hit by the bullet?
 
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  • #2
Look at the information you have. Is there some piece of information that might allow you to get the final velocity?
 
  • #3
the 25cm, I am just not sure how I could use it
 
  • #4
creynaud said:
the 25cm, I am just not sure how I could use it
How fast would you need to throw a stone up for it to reach a height of 25cm? What equations do you know relating to constant acceleration, time, distance traveled etc?
 
  • #5
s=vi(t)+1/2(a)(t)^2
what would i put for time though?
 
  • #6
What is the velocity at the height where it turns around?

Edit: You can also apply energy conservation, which will be less cumbersome.
 
  • #7
creynaud said:
s=vi(t)+1/2(a)(t)^2
what would i put for time though?
There are five SUVAT equations. Each involves four of the variables: distance, initial speed, final speed, time, acceleration. As you note, you do not know what time to use, and you don't need to find it. So use the one equation that does not involve time. Also see Orodruin's reply.
 

1. What is a "Wooden block Momentum problem"?

A "Wooden block Momentum problem" is a physics problem that involves analyzing the motion of a wooden block or object, taking into account its momentum, which is the product of its mass and velocity. This type of problem is often used to demonstrate the laws of motion and conservation of momentum.

2. How do you calculate the momentum of a wooden block?

The momentum of a wooden block can be calculated by multiplying its mass (in kilograms) by its velocity (in meters per second). The formula for momentum is: p = m * v, where p is momentum, m is mass, and v is velocity.

3. What is the law of conservation of momentum?

The law of conservation of momentum states that in a closed system, the total momentum remains constant. This means that the total momentum before an event or interaction is equal to the total momentum after the event or interaction. In other words, momentum cannot be created or destroyed, it can only be transferred between objects.

4. How can the "Wooden block Momentum problem" be solved?

The "Wooden block Momentum problem" can be solved by using the principles of conservation of momentum and applying them to the specific scenario given in the problem. This involves setting up equations, using the formula for momentum, and solving for the unknown variables.

5. What are some real-life applications of the "Wooden block Momentum problem"?

The "Wooden block Momentum problem" can be applied in a variety of real-life situations, such as analyzing the motion of objects in collisions, calculating the force of impact in car crashes, and understanding the behavior of objects in sports such as hockey or billiards. It is also used in engineering and design to ensure the safe and efficient movement of objects and structures.

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