Solved Examples of Impulse Problems: Step-by-Step Guide

📚 Quick Study Guide

• 🍎 Impulse Defined: Impulse ($J$) is the change in momentum of an object. It is a vector quantity.
• 📐 Impulse Formula: $J = \Delta p = p_f - p_i = m(v_f - v_i)$, where $m$ is mass, $v_f$ is final velocity, and $v_i$ is initial velocity.
• 💪 Impulse-Momentum Theorem: Impulse is also equal to the average net force ($F$) acting on an object over a time interval ($\Delta t$): $J = F\Delta t$.
• ⏱️ Units of Impulse: Newton-seconds (N s) or kg m/s.
• 💡 Key Idea: Impulse represents the 'impact' or 'jolt' experienced by an object.

🧪 Practice Quiz

1. A 2 kg ball is traveling at 5 m/s. It bounces off a wall and travels in the opposite direction at 3 m/s. What is the impulse on the ball?
   1. -4 kg m/s
   2. 4 kg m/s
   3. -16 kg m/s
   4. 16 kg m/s
2. A force of 10 N is applied to a box for 2 seconds. What is the impulse on the box?
   1. 5 N s
   2. 10 N s
   3. 20 N s
   4. 0 N s
3. A 0.5 kg object's velocity changes from 2 m/s to 6 m/s. What is the impulse on the object?
   1. 1 N s
   2. 2 N s
   3. 3 N s
   4. 4 N s
4. A baseball (mass = 0.145 kg) is pitched at 40 m/s and hit back at 60 m/s. What is the magnitude of the impulse on the ball?
   1. 2.9 Ns
   2. 14.5 Ns
   3. 8.7 Ns
   4. 1.45 Ns
5. A hockey puck with a mass of 0.115 kg is at rest. A player applies an impulse of 3 Ns to the puck. What is the final speed of the puck?
   1. 13 m/s
   2. 26.1 m/s
   3. 3.45 m/s
   4. 0 m/s
6. A car crashes into a wall. Which of the following changes will decrease the impulse experienced by the car?
   1. Increasing the car's mass
   2. Increasing the car's initial velocity
   3. Increasing the time of impact
   4. Decreasing the time of impact
7. A 1 kg ball is dropped from a height and hits the ground with a speed of 7 m/s. If it bounces back with a speed of 5 m/s, what is the magnitude of the impulse imparted by the ground on the ball?
   1. 2 Ns
   2. 5 Ns
   3. 7 Ns
   4. 12 Ns