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  1. M

    Archimedes' principle

    Homework Statement A rectangular waterproof air mattress is 2.0m long, 0.50mwide and 0.08m thick. It has a mass of 2.0kg and is supporting an additional mass of m, while floating in the water, calculate the mass, m, assuming the density of water is 1000kg/m^3 and density of air is...
  2. M

    Heat and internal energy of water temperature

    so, mgh = mc(T-Ti) then solve for Tf? therefore, mgh = mc(Tf - Ti) gh = cTf - cTi gh + cTi = cTf gh/c + Ti = Tf
  3. M

    Spring compression help

    Thanks for you help! =)
  4. M

    Spring compression help

    So in state 1 there is potential energy, no kinetic energy. State 2 there's kinetic energy, where v is half of the max speed and there's potential energy and that's when we solve for x.
  5. M

    Spring compression help

    at state 2, is it half the compressed state?
  6. M

    Spring compression help

    k. i got the answer, the max speed is 0.28m/s. The next part of the question is, for what value of x does the speed equal one-half the maximum speed. What i did was to solve for x with v = 1/2(max speed) I got the answer wrong. Can someone point out where i went wrong?
  7. M

    Spring compression help

    so 1/2mv^2 = 1/2kx^2 v = square root (kx^2/m)
  8. M

    Spring compression help

    sorry not kinetic energy but potential energy.
  9. M

    Spring compression help

    so KE + KEs = 0 1/2mv^2 + 1/2kx^2 = 0 solve for v?
  10. M

    Spring compression help

    Homework Statement A 0.40kg object connected to a light spring with a force constant of 19.6N/m oscillates on a frictionless horizontal surface. If the spring is compressed 4.0 cm and released from rest, determine (a) the maximum speed of the object. Homework Equations F = -kx The...
  11. M

    Heat and internal energy of water temperature

    so distance isn't included in the equation? and mass?
  12. M

    Heat and internal energy of water temperature

    Homework Statement Water at the top of Niagara Falls has a temperature of 10.0degrees celsius. If it falls a distance of 50.0m and all of its potential energy goes into heating the water, calculate the temperature of the water at the bottom of the falls. Homework Equations W = change...
  13. M

    Use conservation of energy to determine the angular speed of a spool

    k. mass of the spool is not given so how can we solve the KEr??
  14. M

    Use conservation of energy to determine the angular speed of a spool

    potential energy = -mgh change in KEt + change in KEr + change in PE is that right? but what is v in KEt?
  15. M

    Use conservation of energy to determine the angular speed of a spool

    Homework Statement Use conservation of energy to determine the angular speed of a spool after the bucket(3.0kg) has fallen 4.00m, starting from rest. Homework Equations KE = 1/2mv^2 KEr = 1/2 * I * omega^2 PE - mgh The Attempt at a Solution i don't know how to start. I...
  16. M

    Simple problem, but confused with acceleration of gravity

    ok, i tried using that convention, but i get the wrong answer. Going up i used a positive 'a' and if it's falling down, i use a negative 'a' For example for this question, i got it wrong =( A projectile is launched straight up at 60.0m/s from a height of 80m at the edge of a cliff. The...
  17. M

    Simple problem, but confused with acceleration of gravity

    Homework Statement A silo is under construction and a large brick is being hoisted up at a constant speed of 3.2m/s. The rope breaks when the brick is at a height of 28m above the ground. a) find the greatest height reached by the brick. Homework Equations i know which equation to...
  18. M

    Need clarification about x-t and v-t graph

    ok. so basically the negative or positive sign just tells us the direction and not if is speeds or slows down. correct?? i came across this question? If the average velocity of an object at a certain time interval is zero, what is its displacement? What's happening to the object? If the...
  19. M

    Need clarification about x-t and v-t graph

    but does it mean that the object is slowing down?
  20. M

    Need clarification about x-t and v-t graph

    Homework Statement I'm confused with what a negative slope means on an x-t and v-t graph. On an x-t graph, I understand that a positive constant slope means uniform velocity and when the slope is 0, then the object is stationary. On a v-t graph, constant slope means constant acceleration...
  21. M

    Latent heat and phase change question

    but if you look at my first posting...what's the initial temperatures for Qicewater and Qwater? I always get stumped on temperatures and also on phase changes. FOr example, if a block of ice is put into water, the phases are: ice, ice water, water...right?
  22. M

    Latent heat and phase change question

    I know i'm suppose to add up the energies, but I'm not sure about my temperatures. what's the final temperature of the ice? Initial temp is 0 degrees, but what's the final?? is it 80 degrees?
  23. M

    Latent heat and phase change question

    Homework Statement A 100g cube of ice at 0 degrees is dropped into 1.0kg of water that was originally at 80 degrees. What is the final temperature of the water after the ice has melted? Homework Equations Q = ml Q = mc(Tf - Ti) The Attempt at a Solution i'm not sure again about...
  24. M

    Please help calorimetry problem

    Yes, i know about density. To get mass, just multiply density of water and volume given.
  25. M

    Please help calorimetry problem

    Homework Statement What mass of ice at -10.0 degrees celsius is needed to cool a whale's water tank, holding 1.20 x 10^3 m^3 of water, from 20.0 degrees down to a more comfortable 10 degrees. Homework Equations Q = mc *delta T Q = mL The Attempt at a Solution i'm trying to...
  26. M

    How much of an iceberg is beneath the surface Archimedes principle

    Density ice/density water = volume water/volume ice is that rite?
  27. M

    How much of an iceberg is beneath the surface Archimedes principle

    How much of an iceberg is beneath the surface....Archimedes principle Homework Statement Calculate how much of an iceberg is beneath the surface of the ocean, given that the density of ice is 917kg/m^3 and salt water has density 1025kg/m^3. Homework Equations archimedes principle...
  28. M

    Going down a slide CONSERVATION OF ENERGY

    So when do you consider the angles? Only when there is friction?
  29. M

    Going down a slide CONSERVATION OF ENERGY

    Homework Statement Suppose a slide is 35.0 meters high, but is a straight slope, inclined at 45 degrees with respect to the horizontal. a) find the speed of a 60.0kg thrill seeker at the bottom of the slide, assuming no friction. b) if the thrill seeker has a speed of 20.0m/s at the...
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