# Mastering Physics 9.42 - Momentum of rocket/debris

• kramerbaggins
In summary, a 1500 kg weather rocket accelerates upward at 10m/s^2 and explodes after 2.0 seconds. The lighter fragment reaches a maximum height of 530 m and the question asks for the speed of the heavier fragment just after the explosion. Using the equations v_f^2 = v_i^2 + 2*a*s and p_f = 1000*v_f_1 + 500*v_f_2, the initial velocity of the smaller mass fragment is solved for and used to find the initial velocity of the heavier fragment. The answer is expected to be close to 21 m/s, but a rounding error or incorrect number of significant figures may cause an error message in the system.
kramerbaggins

## Homework Statement

A 1500 kg weather rocket accelerates upward at 10m/s^2. It explodes 2.0 s after liftoff and breaks into two fragments, one twice as massive as the other. Photos reveal that the lighter fragment traveled straight up and reached a maximum height of 530 m.

That is the problem.

What was the speed of the heavier fragment just after the explosion?

That is the question.

I solved and got 20.96 m/s. It gives me this error:

You are close. You may have made a rounding error or used the wrong number of significant figures.

## Homework Equations

Using the 10m/s^2 * 2s, i got the v_i to be 20 m/s, p_i then is 30000 kg*m/s.

p_f is 1000*v_f_1 + 500*v_f_2

Used v_f^2 = v_i^2 + 2*a*s on the smaller mass fragment. Used v_f = 0, a = -9.8, s given in problem. Solved for v_i. This v_i is the inital velocity of the fragment, aka its velocity at the end of the explosion.

Set 30000 = 1000*v_f_1 + 500*v_f_2, using v_f_2 from dynamics equation work above. solved for v_f_1.

## The Attempt at a Solution

Last edited:
At a glance, your work seems to be correct. One possibility, as it says, is that you are using the wrong number of significant figures. You have 4, how many appear in the numbers in the problem?

Well Mastering Physics really doesn't care how many are in your answer as long as it is within like .05 or so. I ahve tried two different answer very close to 21, but still nothing

Ive tried from 20.8-21.0, but still wrong. It is from 20-22 I am assuming, but idk

## 1. What is the equation for calculating momentum?

The equation for calculating momentum is p = mv, where p is momentum, m is mass, and v is velocity.

## 2. How do I calculate the momentum of a rocket or debris?

To calculate the momentum of a rocket or debris, you will need to know the mass and velocity of the object. Once you have these values, you can use the equation p = mv to calculate the momentum.

## 3. How does the mass of a rocket or debris affect its momentum?

The mass of a rocket or debris directly affects its momentum. The greater the mass, the greater the momentum will be. This is because momentum is directly proportional to mass.

## 4. Does the velocity of a rocket or debris impact its momentum?

Yes, the velocity of a rocket or debris does impact its momentum. The higher the velocity, the greater the momentum will be. This is because momentum is directly proportional to velocity.

## 5. Can the momentum of a rocket or debris change?

Yes, the momentum of a rocket or debris can change. This can happen if there is a change in mass or velocity. For example, if the mass of a rocket increases, its momentum will also increase. Similarly, if the velocity of a rocket decreases, its momentum will also decrease.

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