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A billiard ball (A) with a mass of 0.165 kg is traveling at 4.2 m/s. It strikes ball B, which is identical to ball A and is stationary. Ball moves on at angle of 25 degrees to the left of its original direction, which ball B moves 65 degrees to the right. a)Draw a vector diagram to show how the law of conservation of momentum could be applied to this situation. b)Write a simplified equation, in terms of mass and the velocity variables, to show how the law of conservation of momentum could be applied to this situation. c)Use the vector diagram and suitable calculation to determine speeds of ball A and ball B after the collision.

Shane Macguire , 12 Years ago
Grade upto college level
anser 1 Answers
Askiitians Tutor Team

To tackle this problem, we need to apply the principles of momentum conservation in a two-dimensional collision scenario. Let’s break it down step by step, starting with the vector diagram and moving through the equations and calculations.

Visualizing the Collision

In a collision between two billiard balls, we can represent their velocities as vectors. Since ball A is moving and ball B is stationary, we can illustrate this with a vector diagram:

  • Draw a horizontal line to represent the initial velocity of ball A (4.2 m/s).
  • From the tip of this vector, draw a line at a 25-degree angle to the left to represent the direction of ball A after the collision.
  • From the origin, draw another line at a 65-degree angle to the right to represent the direction of ball B after the collision.

Label the vectors as follows:

  • Vector A_initial (4.2 m/s)
  • Vector A_final (after collision, at 25 degrees)
  • Vector B_final (after collision, at 65 degrees)

Applying the Conservation of Momentum

The law of conservation of momentum states that the total momentum before the collision equals the total momentum after the collision. For our scenario, we can express this mathematically.

Momentum Equation

Let’s denote:

  • m = mass of each ball = 0.165 kg
  • v_A_initial = initial velocity of ball A = 4.2 m/s
  • v_A_final = final velocity of ball A
  • v_B_final = final velocity of ball B

The equation for conservation of momentum in the x-direction (horizontal) and y-direction (vertical) can be written as:

In the x-direction:

m * v_A_initial = m * v_A_final * cos(25°) + m * v_B_final * cos(65°)

In the y-direction:

0 = m * v_A_final * sin(25°) - m * v_B_final * sin(65°)

Calculating Final Velocities

Now, we can simplify these equations. Since the masses are the same, we can cancel them out:

Horizontal Momentum Equation

4.2 = v_A_final * cos(25°) + v_B_final * cos(65°)

Vertical Momentum Equation

0 = v_A_final * sin(25°) - v_B_final * sin(65°)

From the vertical equation, we can express v_A_final in terms of v_B_final:

v_A_final * sin(25°) = v_B_final * sin(65°)

v_A_final = (v_B_final * sin(65°)) / sin(25°)

Now, substitute this expression for v_A_final into the horizontal momentum equation:

4.2 = ((v_B_final * sin(65°)) / sin(25°)) * cos(25°) + v_B_final * cos(65°

Now, let’s solve for v_B_final:

4.2 = v_B_final * ( (sin(65°) * cos(25°) / sin(25°)) + cos(65°) )

Calculating the trigonometric values:

  • sin(25°) ≈ 0.4226
  • cos(25°) ≈ 0.9063
  • sin(65°) ≈ 0.9063
  • cos(65°) ≈ 0.4226

Substituting these values into the equation:

4.2 = v_B_final * ( (0.9063 * 0.9063 / 0.4226) + 0.4226 )

Calculating the terms:

4.2 = v_B_final * ( 6.049 + 0.4226 )

4.2 = v_B_final * 6.4716

Now, solving for v_B_final:

v_B_final ≈ 4.2 / 6.4716 ≈ 0.649 m/s

Now, substituting v_B_final back to find v_A_final:

v_A_final = (0.649 * sin(65°)) / sin(25°)

v_A_final = (0.649 * 0.9063) / 0.4226 ≈ 1.4 m/s

Final Results

After the collision:

  • Ball A moves at approximately 1.4 m/s at an angle of 25 degrees to the left.
  • Ball B moves at approximately 0.649 m/s at an angle of 65 degrees to the right.

This analysis illustrates how momentum is conserved in a two-dimensional collision, allowing us to determine the final velocities of both balls after impact.

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