Conservation of Momentum: Examining Collisions in a System

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In summary: Thus, the speed of the diver is 1.5 m/s.In summary, in a system with two moving objects, the total momentum is always conserved during a collision. For the second question, the momentum of the swimmer and the rowboat must be equal before and after the collision, and using the equation of momentum (m1v1 = m2v2), we can calculate the speed of the diver to be 1.5 m/s.
  • #1
wakejosh
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two questions actually:

1. In a system with two moving objects, when a collision occurs
between the two objects,
what is conserved?

a. the total kinetic energy is always conserved
b. the total momentum is always conserved
c. the total kinetic energy and total momentum are always conserved
d. neither the kinetic energy nor the momentum is conserved
e. the total momentum is never conserved

-from what I understand B is the right answer, and If the collision was elastic C would be true, but in this case I think B is the right answer because I know in an isolated collision momentum is always conserved.


with this next question I am having trouble finding the equation I need if anyone can point me in the right direction.

2. A 50 kg swimmer dives horizontally off a 75 kg rowboat. If the
speed of the rowboat
immediately after the swimmer dives off is 1.0 m/s, what speed did
the diver leave the
rowboat?
 
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  • #2
any feedback?

ive been trying to figure out the 2nd one and I get something like this

75kg/1 m/s = 75

now do I just divide? 75/50 kg = 1.5 m/s ?
 
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  • #3
wakejosh said:
-from what I understand B is the right answer, and If the collision was elastic C would be true, but in this case I think B is the right answer because I know in an isolated collision momentum is always conserved.
You are correct. (The key word in this question is "always".)

with this next question I am having trouble finding the equation I need if anyone can point me in the right direction.

2. A 50 kg swimmer dives horizontally off a 75 kg rowboat. If the
speed of the rowboat
immediately after the swimmer dives off is 1.0 m/s, what speed did
the diver leave the
rowboat?

What's conserved?
 
  • #4
well, the momentum.

ive been trying to figure out the 2nd one and I get something like this

75kg/1 m/s = 75

now do I just divide? 75/50 kg = 1.5 m/s ?
 
  • #5
Yes. Since momentum is conserved, it must be that 75*1 = 50*(speed of the diver).
 

FAQ: Conservation of Momentum: Examining Collisions in a System

1. What is momentum and how is it defined?

Momentum is a physical quantity that describes the amount of motion an object has. It is defined as the product of an object's mass and velocity. In other words, momentum = mass x velocity.

2. How is momentum different from velocity?

Momentum and velocity are related but distinct concepts. Velocity is the rate of change of an object's position, while momentum is the product of an object's mass and velocity. Velocity is a vector quantity, while momentum is a vector quantity with both magnitude and direction.

3. What are the units of momentum?

The SI unit for momentum is kilogram meters per second (kg·m/s). In other systems, momentum can also be expressed in terms of grams and centimeters per second (g·cm/s) or pounds and feet per second (lb·ft/s).

4. How does momentum affect collisions?

In a collision between two objects, the total momentum before the collision is equal to the total momentum after the collision. This is known as the law of conservation of momentum. Momentum also plays a role in determining the outcomes of collisions, such as the direction and speed of the objects after the collision.

5. How is momentum related to Newton's laws of motion?

Momentum is closely related to Newton's laws of motion, particularly the second law which states that the net force acting on an object is equal to the rate of change of its momentum. This means that an object with a greater momentum will require a larger force to change its motion, and vice versa.

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