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A ball moving with velocity of \(9 \mathrm{~m} / \mathrm{s}\) collides with another similar stationary ball. After the collision both the balls move in directions making an angle of \(30^{\circ}\) with the initial direction. After the collision their speed will be (a) \(2.6 \mathrm{~m} / \mathrm{s}\) (b) \(5.2 \mathrm{~m} / \mathrm{s}\) (c) \(0.52 \mathrm{~m} / \mathrm{s}\) (d) \(52 \mathrm{~m} / \mathrm{s}\)

Short Answer

Expert verified
The speed of each ball after the collision would be approximately \(5.2 \mathrm{~m/s}\), thus the correct answer is (b).

Step by step solution

01

Identify the Initial Condition

Before the collision, the moving ball has a velocity of \(9 \mathrm{~m} / \mathrm{s}\), while the stationary ball has a velocity of \(0 \mathrm{~m} / \mathrm{s}\). This gives an initial momentum of \(9m\), where \(m\) is the mass of the balls.
02

Set Up the Conservation of Momentum

The principle of conservation of momentum states that the total momentum before and after the collision should be the same. Thus, we set up the equation \(m \cdot (9 \mathrm{~m/s}) = 2m \cdot v \cdot \cos(30^{\circ})\), where \(v\) is the velocity of the balls after collision.
03

Solve the Equation

Solving the equation for \(v\) gives us \(v = \frac{9}{2\cos(30^{\circ})} \approx 5.2 \mathrm{~m} / \mathrm{s}\).
04

Match with the Correct Option

Option (b) matches our calculated velocity, thus (b) is the correct answer.

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Key Concepts

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

Collision
In physics, a collision is an event where two or more bodies exert forces on each other over a very short period of time. There are different types of collisions, but the main ones are elastic and inelastic. In an elastic collision, both momentum and kinetic energy are conserved. Meanwhile, in an inelastic collision, only momentum is conserved, meaning some kinetic energy is turned into other forms of energy, such as heat or sound.

**Types of Collisions:**
  • **Elastic Collision:** Both momentum and kinetic energy are conserved.
  • **Inelastic Collision:** Only momentum is conserved. Kinetic energy is not.
  • **Perfectly Inelastic Collision:** The objects stick together post-collision, losing more kinetic energy.
In the exercise you encountered, the collision is between two balls where momentum is conserved. The balls move away from each other at an angle after colliding, showing a typical collision scenario.
Velocity
Velocity is a vector quantity that describes the speed of an object in a particular direction. In the exercise, the ball had an initial velocity of \(9 \mathrm{~m/s}\) before it collided with the stationary ball. After the collision, the new velocities of both balls were calculated.

**Key Points About Velocity:**
  • **Direction Matters:** Unlike speed, velocity includes direction.
  • **Initial versus Final Velocity:** The initial velocity is what an object starts with, and final velocity is what it ends up with after an event like a collision.
  • **Conservation Impacts:** After a collision, stable systems will often show conserved total velocities adjusted by direction and other factors.
The calculated velocities of \(5.2 \mathrm{~m/s}\) post-collision for each ball show how energy is distributed equally in both directions.
Angle of Motion
The angle of motion in a physics problem is crucial to understand because it helps determine the final direction of objects after events like collisions. In this exercise, both balls moved at an angle of \(30^\circ\) relative to the original movement path of the first ball.

**Understanding Angles in Motion:**
  • **Direction Change:** Angles signify how much an object’s path changes post-event.
  • **Influences Calculation:** Angles are used in conservation laws to calculate exact velocities and momenta.
  • **Representation of Forces:** The angle shows how forces are distributed across different axes.
In calculations, it is crucial to convert angles into radians as needed for using trigonometric functions. Here, the cosine of \(30^\circ\) is used to find the post-collision velocity, demonstrating how angles directly influence the physics calculations.
Physics Problem Solving
Physics problem solving involves a structured approach to tackle complex scenarios with logical and mathematical techniques. The process requires understanding the given information and applying relevant physics laws, such as the conservation of momentum.

**Effective Problem-Solving Approach:**
  • **Identify Known and Unknown Variables:** Always start by listing what is already known and what needs to be found.
  • **Apply Relevant Principles:** Choose the right physics laws—conservation laws, in this case.
  • **Construct Equations From Principles:** Use the principles to build equations that relate known and unknown variables.
  • **Solve Systematically:** Break down the big problem into manageable parts to simplify the mathematical process.
By setting up and solving the equation \(m \cdot (9 \mathrm{~m/s}) = 2m \cdot v \cdot \cos(30^{\circ})\), you can effectively find the desired velocities, confirming that problem-solving requires detailed analysis and calculation.

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