1 / 25

Impulse & Momentum

Impulse & Momentum. Physics 11. Problem. A baseball of mass 0.145kg is pitched toward a batter with an initial velocity of 35 m/s. If the batter hits the ball in the opposite direction at 45 m/s, determine the force that is applied by the bat on the ball if the contact time was 0.013s.

yuli-avery
Download Presentation

Impulse & Momentum

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Impulse & Momentum Physics 11

  2. Problem • A baseball of mass 0.145kg is pitched toward a batter with an initial velocity of 35 m/s. If the batter hits the ball in the opposite direction at 45 m/s, determine the force that is applied by the bat on the ball if the contact time was 0.013s.

  3. Impulse • When an object is accelerated, typically the force will only be applied for a given time • So instead of considering Newton’s Second Law as we have previously discussed it, we will rearrange the equation

  4. Use Newton’s Second Law and substitute the definition for acceleration Rearrange the equation so there are no terms in the denominator This expression is known as impulse (J) Impulse

  5. Example • A tennis ball is struck by a racquet with a force of 750N; if the time of contact was 0.023s, what impulse was delivered to the ball?

  6. Momentum can also be defined starting from Newton’s Second Law The rate of change of momentum can also be used to determine the force Momentum is defined as the product of an object’s mass and velocity  1st Law of Motion Momentum

  7. Example • A cyclist is travelling at 32km/h and the bike and rider have a mass of 85kg. What is their momentum?

  8. Impulse and momentum can be related in order to solve dynamics problems Substitute the definition for momentum into the impulse equation Impulse-Momentum

  9. Example – again… • A baseball of mass 0.145kg is pitched toward a batter with an initial velocity of 35 m/s. If the batter hits the ball in the opposite direction at 45 m/s, determine the force that is applied by the bat on the ball if the contact time was 0.013 s.

  10. Example

  11. Collisions Physics 11

  12. Conservation of Momentum • The vector quantity momentum will be conserved in any collision • That is, the sum of all momenta prior to the collision will be equal to the sum of all momenta following a collision • Every object that has mass and velocity will have momentum and must be included in the total momentum of the system

  13. Collisions • With any collision, it is imperative that you diagram the system prior to and following the collision and identify all objects involved in the collision • This allows you to ensure that you calculate the total momentum for the system to properly analyze the situation • While this may seem onerous, generally we will be looking at a maximum of two particles

  14. Recall Momentum • Momentum • Impulse

  15. Momentum Conservation • Momentum is conserved • This is an expression of Newton’s first law: • “An object at rest or in uniform motion will remain at rest or in uniform motion unless acted on by an external force.” • External forces can change the momentum of a system (Impulse)

  16. Momentum Conservation • In interactions between two bodies, momentum of one object can change, but the total momentum of the system remains constant.

  17. Types of Momentum Problems • Elastic collisions • Inelastic collisions • Explosions Final Initial Final Initial Initial Final

  18. Explosions: Recoil • A Barrett M82 is a high calibre sniper rifle. Below are it’s specifications: • Barrel length: 73.7 cm • Weight: 14.0 kg • Muzzle Velocity: 853 m/s • Typical ammunition weight: 50.0g • Calculate the magnitude force exerted on the riflemen.

  19. Explosion: Recoil • The plan is this • Calculate the momentum of the rifle knowing the momentum of the bullet • Calculate the impulse imparted to the riflemen to stop the gun. • Impulse is change in momentum • Impulse is force multiplied by time • Need to know the time (how long) the explosion takes.

  20. The Momentum Problem • Barrel length: 73.7 cm • Weapon mass: 14.0 kg • Muzzle Velocity: 853 m/s • Typical ammunition mass: 50.0g

  21. Impulse • We know the person stops the gun, so to find the force, we need to know the interaction time.

  22. Explosions: Recoil • Barrel length: 73.7 cm • Weapon mass: 14.0 kg • Muzzle Velocity: 853 m/s • Typical ammunition mass: 50.0g

  23. Bring it all together

  24. For Comparison • How many people would have to sit on your shoulder to get the same force?

  25. Collision • A billiard ball, mass 155g, is travelling at 3.5m/s across the table. It strikes another ball at rest, mass 150g and comes to rest. What is the velocity of the second ball after the collision?

More Related