/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 117 A collision occurs between a \(2... [FREE SOLUTION] | 91Ó°ÊÓ

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A collision occurs between a \(2.00 \mathrm{~kg}\) particle traveling with velocity \(\vec{v}_{1}=(-4.00 \mathrm{~m} / \mathrm{s}) \hat{\mathrm{i}}+(-5.00 \mathrm{~m} / \mathrm{s}) \mathrm{j}\) and a \(4.00 \mathrm{~kg}\) particle traveling with velocity \(\vec{v}_{2}=(6.00 \mathrm{~m} / \mathrm{s}) \hat{\mathrm{i}}+(-2.00 \mathrm{~m} / \mathrm{s}) \hat{\mathrm{j}} .\) The collision connects the two particles. What then is their velocity in (a) unit- vector notation and as a (b) magnitude and (c) angle?

Short Answer

Expert verified
The final velocity is \(2.67\hat{i} - 3.00\hat{j}\) m/s, magnitude is 4.00 m/s, and angle is \(-48.37^\circ\).

Step by step solution

01

Understand the Problem

We need to find the final velocity of two particles after a collision, where they stick together. The particles have masses of \(2.00 \text{ kg}\) and \(4.00 \text{ kg}\), with initial velocities \(\vec{v}_1\) and \(\vec{v}_2\). We aim to find the final velocity vector in unit-vector notation, its magnitude, and the angle it makes with the positive x-axis.
02

Calculate Total Momentum Before Collision

Calculate the total momentum before the collision using the formula \( \textbf{p} = m \times \vec{v} \). The momentum of particle 1 is \( \vec{p}_1 = 2.00 \times (-4.00\hat{i} - 5.00\hat{j}) \) and for particle 2 is \( \vec{p}_2 = 4.00 \times (6.00\hat{i} - 2.00\hat{j}) \).
03

Find Momentum of Each Particle

For particle 1: \( \vec{p}_1 = (-8.00\hat{i} - 10.00\hat{j}) \text{ kg} \cdot \text{m/s}\). For particle 2: \( \vec{p}_2 = (24.00\hat{i} - 8.00\hat{j}) \text{ kg} \cdot \text{m/s}\).
04

Calculate Total Initial Momentum

Add the momenta of both particles: \( \vec{p}_{\text{total}} = \vec{p}_1 + \vec{p}_2 = (-8.00 + 24.00)\hat{i} + (-10.00 - 8.00)\hat{j} \). This simplifies to \( \vec{p}_{\text{total}} = 16.00\hat{i} - 18.00\hat{j} \text{ kg} \cdot \text{m/s} \).
05

Apply Conservation of Momentum

Since momentum is conserved, \( \vec{p}_{\text{total}} = (m_1 + m_2) \cdot \vec{v}_f \). Here, \( m_1 + m_2 = 6.00 \text{ kg} \). Using \( \vec{v}_f = \frac{\vec{p}_{\text{total}}}{m_1 + m_2} \), we substitute \( \vec{p}_{\text{total}} = 16.00\hat{i} - 18.00\hat{j} \) and \( 6.00 \text{ kg} \) in the equation.
06

Solve for Final Velocity Vector

Calculate \( \vec{v}_f = \frac{16.00}{6.00}\hat{i} - \frac{18.00}{6.00}\hat{j} \). Therefore, \( \vec{v}_f = 2.67\hat{i} - 3.00\hat{j} \text{ m/s} \).
07

Calculate Magnitude of the Velocity

Use the formula \( |\vec{v}_f| = \sqrt{(v_{fx})^2 + (v_{fy})^2} \) where \( v_{fx} = 2.67 \) m/s and \( v_{fy} = -3.00 \) m/s. This gives \( |\vec{v}_f| = \sqrt{(2.67)^2 + (-3.00)^2} \approx 4.00 \text{ m/s} \).
08

Calculate Angle of Velocity Vector

Find the angle \( \theta = \tan^{-1}\left(\frac{v_{fy}}{v_{fx}}\right) \). Substituting the values, \( \theta = \tan^{-1}\left(\frac{-3.00}{2.67}\right) \), which calculates to \( \theta \approx -48.37^\circ \). The negative sign indicates the angle is below the positive x-axis.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Collision Mechanics
In the study of collision mechanics, understanding the interaction between two objects in motion is key. Collisions can be classified into elastic and inelastic. An elastic collision retains kinetic energy; no energy is lost as heat or sound. Conversely, in an inelastic collision, such as the one in our exercise, the colliding particles stick together and lose kinetic energy. This collision conserves momentum but not necessarily kinetic energy.
The collision described in our exercise is inelastic because the two particles connect post-impact. This scenario requires us to focus on conserving linear momentum while anticipating changes in internal energies. Recognizing the type of collision helps decide which physical laws to apply for solving problems related to post-collision velocities.
Vector Notation
Vectors, represented by arrows, depict mathematical quantities with both magnitude and direction. In physics, particularly in collision problems like ours, vectors are essential for expressing and solving conditions involving velocities and forces.
  • Velocity vectors describe how fast and in which direction a particle is moving in a coordinate system, often listed as components along the x and y axes.
  • By using vector notation, we can efficiently add or subtract these components to analyze motion before and after collisions.

This structured approach, using unit-vector notation like \((v_x \hat{i} + v_y \hat{j})\) to express velocity, simplifies underlying calculations and provides a clear representation of motion's directional aspects.
Momentum Calculation
Momentum is a fundamental concept in physics denoted by the symbol \( extbf{p} \), calculated as the product of an object's mass and velocity (\( \textbf{p} = m \times \vec{v} \)).
  • For our collision, calculating the initial momentum involves multiplying each particle's mass by its corresponding velocity vector. This gives us the momentum for each particle prior to the collision.
  • After the particles stick together, total momentum is calculated by adding the momentum vectors of both particles. This step involves straightforward arithmetic operations on vector components.

Once calculated, the total momentum directly leads to the final velocity of the combined particles, leveraging the principle of conservation of momentum to maintain the momentum before and after the collision.
Physics Problem Solving
Physics problem solving involves a series of methodological steps. When addressing a problem like the collision exercise, it’s crucial to:
  • Begin with understanding the given information and what needs to be determined.
  • Use fundamental physics principles like conservation laws to guide your solution process.
  • Translate physical scenarios into mathematical equations, utilizing tools such as vector notation and momentum calculations.
  • Perform calculations with care, maintaining unit consistency and checking results for logical coherence.

Solving physics problems is not just about calculations; it is about interpreting results to make sense of physical phenomena. For instance, determining the final velocity vector in magnitude and direction not only concludes the calculation but provides insights into the motion post-collision.

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Most popular questions from this chapter

A \(0.550 \mathrm{~kg}\) ball falls directly down onto concrete, hitting it with a speed of \(12.0 \mathrm{~m} / \mathrm{s}\) and rebounding directly upward with a speed of \(3.00 \mathrm{~m} / \mathrm{s}\). Extend a \(y\) axis upward. In unit- vector notation, what are (a) the change in the ball's momentum, (b) the impulse on the ball, and (c) the impulse on the concrete?

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