Collision question - Simple one

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In summary, the conversation was about a physics problem involving a 65kg boy and a 40kg girl on roller blades. The girl pushes the boy with a velocity of 2.9 m/s, and the question is asking for the speed of the girl after the push. The attempted solution using the equation m1(v1i - v1f) = m2(v2f - v2i) resulted in a speed of 3.9 m/s, but the correct answer is 4.71 m/s. After some back and forth, it was discovered that the error was due to mistaking a 4 for a 9 on the keyboard.
  • #1
nukeman
655
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Homework Statement



Something I am doing wrong?

"A 65kg boy and his 40kg sister both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backwards with a velocity of 2.90 m/s toward the west. Ignore friction.

What speed does the girl go?"

I cam up with m1(v1i - v1f) = m2(v2f - v2i)

Solved for v2f and got 3.9 m/s

But the correct answer is 4.71 m/s

?? Any help?



Homework Equations





The Attempt at a Solution

 
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  • #2
nukeman said:

Homework Statement



Something I am doing wrong?

"A 65kg boy and his 40kg sister both wearing roller blades, face each other at rest. The girl pushes the boy hard, sending him backwards with a velocity of 2.90 m/s toward the west. Ignore friction.

What speed does the girl go?"

I cam up with m1(v1i - v1f) = m2(v2f - v2i)

Solved for v2f and got 3.9 m/s

But the correct answer is 4.71 m/s

?? Any help?



Homework Equations





The Attempt at a Solution


m1 * v1 = m2 * v2
where
m1 = 65
v1 = 2.9
m2 = 40
v2 = ?
 
  • #3
what the heck, I am still getting 3.9 :(

im going (65)(2.4)=(40)(x) solve for x, which = 3.9
 
  • #4
You should have a 2.9 instead of your 2.4 :)
 
  • #5
JHamm said:
You should have a 2.9 instead of your 2.4 :)

I imagine he's beating his head on his keyboard right about now...:-p
 
  • #6
Haha, Dave, yes I was!

Thanks, I guess my 4's look way too much like 9's :)
 
  • #7
nukeman said:
Haha, Dave, yes I was!

Thanks, I guess my 4's look way too much like 9's :)

on ... your ... keyboard ? :bugeye:
 

FAQ: Collision question - Simple one

What is a collision question?

A collision question is a type of simple question that involves two objects or concepts colliding or coming into contact with each other. It is often used in physics and other scientific fields to analyze the effects of collisions on different systems.

What factors affect the outcome of a collision?

The outcome of a collision can be affected by several factors, including the mass, velocity, and direction of the objects involved, as well as the type of collision (elastic or inelastic) and any external forces acting on the system.

How is momentum conserved in a collision?

Momentum, which is the product of an object's mass and velocity, is conserved in a collision. This means that the total momentum of the system before and after the collision remains the same, regardless of any changes in individual object velocities.

What is the difference between an elastic and inelastic collision?

An elastic collision is one in which the total kinetic energy of the system is conserved, meaning that the objects bounce off each other without losing any energy. In an inelastic collision, some of the kinetic energy is lost and the objects may stick together or deform upon impact.

How can collisions be analyzed mathematically?

Collisions can be analyzed using equations that relate the initial and final velocities of the objects, as well as their masses and any external forces. These equations can help determine the outcome of a collision and provide insights into the physical principles at play.

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