Solve Collision Questions: Cannonball Speed & Dog Mass

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The discussion revolves around solving two physics problems involving conservation principles. The first problem involves a cannon and a cannonball, where the cannon's recoil velocity is used to determine the cannonball's speed. The second problem examines a dog jumping onto a moving cart, requiring the calculation of the dog's mass based on the cart's new speed after the jump. Participants express uncertainty about which equations to apply, emphasizing the conservation of momentum as the underlying principle. The conversation highlights the importance of understanding these conservation laws in solving collision-related questions.
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1. Jamie and Adam fire a cannon with a mass of 1150 kg. As the 14.5 kg cannonball leaves the cannon, the cannon recoils with a velocity of 1.75 m/s. How fast does the cannonball fly?

2. A 45 kg cart rolls along a railroad track at 4.0 m/s. A dog running at 7.6 m/s to catch up with the cart jumps on the cart. After the dog jumps on the cart, the cart is moving at 6.0 m/s. What is the mass of the dog?

2. m1v1 + m2v2 = (m1+m2)Vf

m1v1 + m2v2 = m1v1 + m2v2

(m1 + m2)*Vi = m1v1 + m2v2

3. I'm not sure what equation to use...
 
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rainy365days said:
1. Jamie and Adam fire a cannon with a mass of 1150 kg. As the 14.5 kg cannonball leaves the cannon, the cannon recoils with a velocity of 1.75 m/s. How fast does the cannonball fly?

2. A 45 kg cart rolls along a railroad track at 4.0 m/s. A dog running at 7.6 m/s to catch up with the cart jumps on the cart. After the dog jumps on the cart, the cart is moving at 6.0 m/s. What is the mass of the dog?


2. m1v1 + m2v2 = (m1+m2)Vf

m1v1 + m2v2 = m1v1 + m2v2

(m1 + m2)*Vi = m1v1 + m2v2


3. I'm not sure what equation to use...
Do you know what principle those equations are based on ?
 
SammyS said:
Do you know what principle those equations are based on ?

Collision? I'm sorry, I'm not exactly sure what you're asking.
 
rainy365days said:
Collision? I'm sorry, I'm not exactly sure what you're asking.

They're based on conservation of something .

Do you know what that something is?
 
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Kindly see the attached pdf. My attempt to solve it, is in it. I'm wondering if my solution is right. My idea is this: At any point of time, the ball may be assumed to be at an incline which is at an angle of θ(kindly see both the pics in the pdf file). The value of θ will continuously change and so will the value of friction. I'm not able to figure out, why my solution is wrong, if it is wrong .
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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