Math Problem Statement

An iron ball of mass 2 kg moving horizontally hits a wall with a velocity of 5 m/s perpendicularly and rebounds with a velocity of 3 m/s. What is the magnitude of the applied force?

Solution

To calculate the magnitude of the applied force, we need to find the impulse delivered during the collision and then use the relationship between impulse and force.

Steps to Solve:

  1. Impulse Formula: Impulse (JJ) is the change in momentum of the ball: J=Δp=mΔvJ = \Delta p = m \cdot \Delta v

  2. Initial and Final Momentum:

    • Initial velocity: vi=5m/sv_i = 5 \, \text{m/s} (toward the wall).
    • Final velocity: vf=3m/sv_f = -3 \, \text{m/s} (rebounding from the wall; negative because direction has changed).
    • Change in velocity: Δv=vfvi=35=8m/s.\Delta v = v_f - v_i = -3 - 5 = -8 \, \text{m/s}.
    • Change in momentum: Δp=mΔv=2(8)=16kg\cdotpm/s.\Delta p = m \cdot \Delta v = 2 \cdot (-8) = -16 \, \text{kg·m/s}. (Magnitude of impulse: J=16kg\cdotpm/s|J| = 16 \, \text{kg·m/s}).
  3. Relation to Force: The force is related to impulse through the equation: J=FΔtJ = F \cdot \Delta t Rearrange to solve for force: F=JΔt.F = \frac{J}{\Delta t}.

  4. Assumption About Time (Δt\Delta t): If the time of contact (Δt\Delta t) is not given, the applied force cannot be determined directly. For example:

    • If Δt=0.1s\Delta t = 0.1 \, \text{s}, then: F=160.1=160N.F = \frac{16}{0.1} = 160 \, \text{N}.

Thus, the magnitude of the force depends on the collision duration. Please provide the collision time to calculate the force, or we can conclude that the impulse magnitude is 16 kg·m/s.


Would you like more details about impulse and momentum? Here are 5 related questions to expand your understanding:

  1. What is the relationship between impulse and force in a practical situation?
  2. How does the direction of momentum affect the final calculations?
  3. How can we measure the time of contact during a collision in real-life experiments?
  4. What happens to the kinetic energy in this collision—was it elastic or inelastic?
  5. How would the force change if the mass of the ball doubled?

Tip: Always pay attention to directions when working with vector quantities like velocity and momentum.

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Math Problem Analysis

Mathematical Concepts

Physics
Impulse and Momentum
Forces
Vector Quantities

Formulas

Impulse (J) = Δp = m × Δv
Force (F) = J / Δt

Theorems

Newton's Second Law of Motion
Conservation of Momentum

Suitable Grade Level

Grades 9-12