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Collision Forces and Acceleration in Car-Truck Collisions

Explore the impact forces and acceleration in car-truck collisions based on Newton's Third Law of Motion. Understand the concept of action and reaction forces, as well as the conservation of momentum. Practice problems provided for better understanding.

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Collision Forces and Acceleration in Car-Truck Collisions

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  1. Question 4.14aCollision Course I a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each A small car collides with a large truck. Which experiences the greater impact force?

  2. Question 4.14bCollision Course II a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each In the collision between the car and the truck, which has the greater acceleration?

  3. Newton’s 3rd Law of Motion “For every action force there is an equal, but opposite, reaction force” What is an Action Force? What is a Reaction Force? What examples can you think of? Read pages 48-49 

  4. 3rd Law Examples • Action force: • Force of hand pulling up on briefcase handle • Reaction force: • Force of briefcase pulling down on hand • Action Force: • Force of Earth’s gravitational pull down on briefcase • Reaction Force: • Force of briefcase’s gravitational pull up on the Earth

  5. Question 4.14aCollision Course I a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each A small car collides with a large truck. Which experiences the greater impact force?

  6. Question 4.14aCollision Course I a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each A small car collides with a large truck. Which experiences the greater impact force? According to Newton’s Third Law, both vehicles experience the same magnitude of force.

  7. Question 4.14bCollision Course II a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each In the collision between the car and the truck, which has the greater acceleration?

  8. Question 4.14bCollision Course II a) the car b) the truck c) both the same d) it depends on the velocity of each e) it depends on the mass of each In the collision between the car and the truck, which has the greater acceleration? We have seen that both vehicles experience the same magnitude of force. But the acceleration is given byF/mso thecarhas thelarger acceleration, because it has thesmaller mass.

  9. Let’s think about collisions: • How can 2 objects collide, and what can happen when they do? • Head-on, Rear-end, both moving, only one moving… • They could bounce off each other • They could stick together • Anything else?

  10. Let’s start with 1 object… • Colliding with a wall • What’s happening during that collision? • How can we quantify values, such as the impact force, experienced during collision? • Impulse-Momentum!

  11. a) the superball b) the blob of clay c) it doesn’t matter—they will be equally effective Question 6.17Shut the Door! You are lying in bed and you want to shut your bedroom door. You have a superball and a blob of clay (both with the same mass) sitting next to you. Which one would be more effective to throw at your door to close it?

  12. a) the superball b) the blob of clay c) it doesn’t matter—they will be equally effective Question 6.17Shut the Door! You are lying in bed and you want to shut your bedroom door. You have a superball and a blob of clay (both with the same mass) sitting next to you. Which one would be more effective to throw at your door to close it? The superball bounces off the door with almost no loss of speed,so its Dp (and that of the door) is 2mv. The clay sticks to the door and continues to move along withit,so its Dp is less than that of the superball, and therefore it imparts less Dp to the door.

  13. During a collision between 2 things: • The time the two objects are in contact with each other is exactly the same The Force each object experiences is exactly the same—WHY? Newton’s 3rd Law of Motion

  14. During a collision between 2 things: • So, What does Newton’s 3rd law tell us about the colliding objects’ changes in momentum? • They’re the same magnitude (but in opposite directions)!

  15. Let’s go one step further… • What does this equation tell us, conceptually?

  16. Conservation of Linear Momentum As long as there is no outside force acting on the objects, within a system of masses the total vector sum of their momenta must remain constant. In other words, momentum must be conserved Total momentum BEFORE a collision or explosion (an event) will be the same as the total momentum AFTER the collision or explosion Impulse-Momentum will give us a picture of what happens DURING the collision

  17. Example: • A rail truck of mass 4.50 x 103 kg is moving at a speed of 1.80 m·s-1 when it collides with a stationary truck of mass 1.50 x 103 kg. The two trucks couple together. What is the velocity of the trucks immediately after the collision?

  18. Practice #2 • Stone A of mass 0.50 kg is sliding at 3.8 m·s-1 across the surface of a frozen pond when it collides with a stationary stone B of mass 3.00 kg. After the collision, stone B moves off at a speed of 0.65 m·s-1 in the same original direction as stone A’s initial velocity. What is the final velocity of stone A?

  19. The engine of a rocket ejects gas at high speed, as shown below. The rocket accelerates forwards because A. the momentum of the gas is equal but opposite in direction to the momentum of the rocket. B. the gas pushes on the air at the back of the rocket. C. the change in momentum of the gas gives rise to a force on the rocket. D. the ejected gas creates a region of high pressure behind the rocket.

  20. A fan and a sail are mounted vertically on a cart that is initially at rest on a horizontal table as shown: When the fan is turned on an air stream is blown towards the right and is incident on the sail. The cart is free to move with negligible resistance forces. After the fan has been turned on the cart will A. move to the left and then to the right. B. remain at rest. C. move towards the right. D. move towards the left.

  21. Types of Collisions

  22. Explosions! • When 2 (or more) objects that are initially traveling together as one item push apart from each other • Sum of the momenta of each object after the explosion is equal to the initial momentum of the original combination. • Examples: • Two skaters, initially at rest, pushing off from each other and move in opposite directions as the other • Fireworks (a lot more than 2 pieces in the end…) • Rocket blasting off

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