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The force on a bullet and the force on the gun is same when the gun is fired, yet the bullet and the gun have very different accelerations? Why is this?

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Presentation on theme: "The force on a bullet and the force on the gun is same when the gun is fired, yet the bullet and the gun have very different accelerations? Why is this?"— Presentation transcript:

1 The force on a bullet and the force on the gun is same when the gun is fired, yet the bullet and the gun have very different accelerations? Why is this? Demo with spring carts first!!!! Then on board with m and a

2 Mgun x Agun = Mbullet x Abullet
Remember Force = mass x acceleration Force gun= Force bullet Mgun x Agun = Mbullet x Abullet The bullet has a much greater acceleration due to its small mass/inertia Q – Why aren’t bullets as massive as guns? Q- What would happen if you fired a gun on a skateboard? Carts Put in numbers Less inertia – greater accel do numbers for bullet gun really massive bullet – telly story of shotgun

3 How does a rocket work? Rockets shoot molecular balls of gas
A rocket is a reaction engine! Rocket pushes gas out and gas pushes rocket Rockets shoot molecular balls of gas The rocket pushes on the gas molecules and the gas molecules push back with the same force. Because there is a small mass to each gas molecule you need to push them out with a great acceleration which requires a great force (explosion) Because the gas has a large force on it, the gas pushes the rocket back with the same large force By increasing the amount of gas shot out per second, you increase the mass of gas To accelerate a larger mass of gas requires a greater force and thus a larger reaction force Q- Do Rockets require air to accelerate? Alcohol cannon w/ and w/o stopper

4 Cool Shuttle Facts If water, instead of fuel, were pumped by the three Space Shuttle Main Engines, an average family-sized swimming pool could be drained in 25 seconds It only takes the Space Shuttle about 8 minutes to accelerate to its orbital speed of more than 17,000 miles per hour. The Space Shuttle main engine mass is 1/7th as much as a train engine, but delivers as much force as 39 train engines. Hero’s engine Video of nasa launch

5 Assessment Imagine you are jumping off a small boat on a frictionless water surface onto the shore. What happens? Do you move forward? Why?


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