Momentum Problems: Help with 2 Problems and Energy Stored in Spring

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In summary, the conversation discusses two momentum problems and the users are seeking help and clarification on how to solve them. The first problem involves a child on a sled throwing a snowball, and the second problem involves blocks and a spring. The users also express their appreciation for the concept of online homework help.
  • #1
lucifer
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momentum problems

it's be really cool if someone could help me out with the following two momentum problems. nothing much just enough to get me started. i have ideas but I'm not quite sure about what's the right way to go about doing them. also want to say hi to all the people here. must say the whole homework help thing is a very neat concept. :biggrin:

problem 1- A 25 kg child is in a 10 kg sled that travels 1m/s east on ice. The child throws a 3 kg snowball at 40m/s at an angle of 50 degrees north of east. Find the velocity of the sled after the snowball leaves the child's hand.



problem 2- A 2kg block and an 8-kg block are both attached to an ideal spring (for which k=200 N/m) and both are initially at rest on a horizontal frictionless surface.

In an initial experiment, a 0.1 kg ball of clay is thrown at the 2kg block. The clay is moving horizontally with speed v when it hits and sticks to the block. the 8-kg block is held still by a removable stop. As a result, the spring compresses a maximum distance of 0.4 meters. Find:

a) the energy stored in the spring at max compression.

b) speed of the clat ball and 2-kg block immediately after the clay sticks to the block but before the spring compresses significantly.

c) the initial speed v of the clay.
 
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  • #2
lucifer said:
problem 1- A 25 kg child is in a 10 kg sled that travels 1m/s east on ice. The child throws a 3 kg snowball at 40m/s at an angle of 50 degrees north of east. Find the velocity of the sled after the snowball leaves the child's hand.
Use conservation of momentum. I think you have to assume the 3 kg snowball was part of the sled+child system before the kid threw it.
The initial momentum is (25+10)1=35 kg m/s in the (say) x-direction.
The final momentum is equal to this.
Find the momentum of the snowball and the sled+kid which now weighs 32 kg together.
 
  • #3
problem 2

a) it's just E = 1/2kx^2 = 1/2k(0.4)^2 J
b) & c) I couldn't really understand the question but I think it has something to do with the Kinetic Energy being transformed into Elastic Energy which means that 1/2kx^2 = 1/2mv^2
 
  • #4
thanks a lot for the replies, Galileo and futb0l. it was due today and i got it done(eventually) but i had to ask my friend to help me out in lunch.
 

FAQ: Momentum Problems: Help with 2 Problems and Energy Stored in Spring

What is momentum and how is it calculated?

Momentum is a measure of an object's motion and is defined as the product of its mass and velocity. It is calculated using the equation p = m * v, where p is momentum, m is mass, and v is velocity.

Can momentum be conserved in a closed system?

Yes, according to the law of conservation of momentum, the total momentum of a closed system remains constant, meaning it is conserved. This means that the total momentum before and after a collision or interaction will be the same.

How do you solve for momentum in a problem involving two objects colliding?

To solve for momentum in a collision problem, you can use the equation m1v1 + m2v2 = (m1 + m2)v', where m1 and v1 are the mass and velocity of the first object, m2 and v2 are the mass and velocity of the second object, and v' is the final velocity of the combined objects after the collision.

How does the energy stored in a spring change as it is stretched or compressed?

The energy stored in a spring is directly proportional to the amount it is stretched or compressed. This means that as the spring is stretched or compressed, the energy stored in it will increase or decrease accordingly.

How is the energy stored in a spring calculated?

The energy stored in a spring can be calculated using the equation PE = 0.5 * k * x^2, where PE is the potential energy stored in the spring, k is the spring constant, and x is the displacement of the spring from its equilibrium position.

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