Another conservation of momentum

In summary, the issue of the New York Times weighed 5.4 kg and was thrown forward by a skateboarder at a speed of 7.4m/s. The skateboarder, who had a combined mass of 50.0kg with the skateboard, was thrown backwards at a speed of 1.4m/s. The initial velocity of both the skateboarder and the newspaper can be calculated using the equation 1. msvs,i + mnvn,i= msvs,f + mnvn,f = 50(vi+vi2)= (44.6)(-1.4)+(5.4)(7.4) = -22.48m/s. This equation assumes that the skateboard is frictionless
  • #1
The issue of the New York Times had a mass of 5.4 kg. Suppose a skateboarder picks up a copy of this issue to have a look at the comic pages while rolling backward on the sakteboard. Upon realizing that the New York Times doesn't have a "funnies" section, the skateboarder promptly throws the entire issue in a recycling container. The newspaper is thrown forward with a speed of 7.4m/s. When the skater throws the newspaper away, he rolls backwards at a speed of 1.4m/s. If the combined mass of the skateboarder and the skateboard is 50.0kg, what is the initial velocity of the skateboarder and newspaper?

I don't know if it's asking for the combined Vi of the skateboarder and the newspaper or if it's asking for each. This is what I did though

1. msvs,i + mnvn,i= msvs,f + mnvn,f = 50(vi+vi2)= (44.6)(-1.4)+(5.4)(7.4)
2. 50(vi+vi2) = -22.48
3. -22.48/50= -.4496

I don't know if that's right, but I have no idea how to do it! help please!
 
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  • #3
is the skateboard frictionless?
 
  • #4
That looks about right. I am not sure about the math though. I trust you can check that yourself. It is not necessary to separate the initial velocities of the skateboarder and the newspaper like you did, since they are essentially the same thing. Thats what its asking really, don't get confused about it.

It be really nice if you could clean up your equations in a more readable way though...
 

What is the conservation of momentum?

The conservation of momentum is a fundamental principle in physics that states that the total momentum of a closed system remains constant, meaning that the combined mass and velocity of all objects in the system will not change unless acted upon by an external force.

What is another conservation of momentum?

Another conservation of momentum is the angular momentum conservation, which states that the total angular momentum of a closed system remains constant, meaning that the combined rotational inertia and rotational velocity of all objects in the system will not change unless acted upon by an external torque.

How is the conservation of momentum related to Newton's third law of motion?

The conservation of momentum is directly related to Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. This means that when two objects interact, the total momentum of the system remains constant, with one object gaining momentum while the other loses an equal amount of momentum in the opposite direction.

What are some real-life examples of the conservation of momentum?

Some real-life examples of the conservation of momentum include a ball bouncing off a wall, a rocket launching into space, and a skateboarder performing a trick on a half-pipe. In all of these examples, the total momentum of the system remains constant, with the objects involved gaining and losing momentum in opposite directions.

How is the conservation of momentum important in fields other than physics?

The conservation of momentum is important in many fields other than physics, including engineering, astronomy, and even sports. For example, engineers use the principle of conservation of momentum to design efficient and safe structures and devices. Astronomers use it to explain the movement of planets and celestial bodies. And athletes use it to optimize their performance in sports such as figure skating and diving.

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