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  1. M

    Simple Magnetic Field Increase/Decrease question.

    Thank you very much. I now understand the concepts of Lenz's law and magnetic fields much better, and I was able to obtain the correct answer. :)
  2. M

    Voltage across parallel switches

    The 300 micro-Farad capacitor in the figure is initially charged to 110 V , the 1200 micro-Farad capacitor is uncharged, and the switches are both open. What is the maximum voltage to which you can charge the 1200 micro-Farad capacitor by the proper closing and opening of the two switches? I...
  3. M

    Simple Magnetic Field Increase/Decrease question.

    So, the x's in the picture represent the original magnetic field, right? I assume that means the induced magnetic field (which should point out of the page) is not shown. Lenz's law says that the induced magnetic field changes in response to an induced current. I don't understand how the...
  4. M

    Simple Magnetic Field Increase/Decrease question.

    33.6 There is a ccw-induced current in the conducting loop shown in the figure. Is the magnetic field inside the loop increasing in strength, decreasing in strength, or steady? I don’t understand if the problem is referring to the induced magnetic field or the pre-existing magnetic...
  5. M

    Clarification on electric potential and kinetic energy

    One form of nuclear radiation, beta decay, occurs when a neutron changes into a proton, an electron, and a chargeless particle called a neutrino: n -> (p+) + (e-) + tex]\upsilon[/tex] where nu is the symbol for a neutrino. When this change happens to a neutron within the nucleus of an atom, the...
  6. M

    Electric potential of four charges

    QUOTE: Remember that the potential energy term on the left was from all four particles. Ah! Thank you! I now have the correct answer!
  7. M

    Electric potential of four charges

    There are four spheres arranged as the four corners of a square, each sphere having a charge of 10 nC and seperated from each other by a distance of 1 cm. The four 1.0 g spheres are released simultaneously and allowed to move away from each other. What is the speed of each sphere when they are...
  8. M

    Equation for molar specific heat

    n_1 moles of a monatomic gas and n_2 moles of a diatomic gas are mixed together in a container. Derive an expression for the molar specific heat at constant volume of the mixture. Expression must be in terms of n_1, n_2, and the gas constant R. I know that the molar specific heat of the...
  9. M

    Buoyant force on a steel boat

    Got it! I made an error in the above calculation when typing it in. I fixed it, and got the correct answer. Thank you for your help!
  10. M

    Buoyant force on a steel boat

    The weight of the boat is equal to the weight of the base (rho*v*g) plus the weight of the sides (rho*v*g). The volume of the sides is equal to 0.187x, where x is the height of the sides. So the weight of the boat is 216776 + 14477.5x, and this is the weight of the water displaced. The volume of...
  11. M

    Venturi tube calculation

    Air flows through this tube at a rate of 1200 cm^3/sec. Assume that air is an ideal fluid. What is the height h of mercury (in cm) in the right side of the U-tube? In case the picture doesn't show up, the tube is a Venturi tube. Wide end has diameter of 2cm, narrow diameter is 4 mm, and...
  12. M

    Buoyant force on a steel boat

    I don't quite understand. The water displaced will not hold the weight of the metal base (7*10*0.4), so how could adding weight onto the boat make it float if it doesn't increase the surface area? I'm picturing a rectangular base with four sides that extend upwards, forming an open-topped box...
  13. M

    Simple volume flow rate calculation

    Got it. I was off by a factor of 10. Thanks
  14. M

    Simple volume flow rate calculation

    [SOLVED] Simple volume flow rate calculation A 1.0-cm-diameter pipe widens to 2.0 cm, then narrows to 0.5 cm. Liquid flows through the first segment at a speed of 4.0m/s. The speed in the second segment is 1m/s, and the speed in the 3rd segment is 16 m/s I thought that volume flow rate was...
  15. M

    Buoyant force on a steel boat

    [SOLVED] Buoyant force on a steel boat The bottom of a steel "boat" is a 7.00 m \times 10.0 m \times 4.00 cm piece of steel ( \rho _{{\rm steel}}=7900\;{\rm kg}/{\rm m}^{3}). The sides are made of 0.550 cm-thick steel. What minimum height must the sides have for this boat to float in...
  16. M

    Rotational Kinetic energy in a loop

    Thanks for the help, Shooting star. I was able to solve the problem. And, sorry FedEx, I have no idea what you're talking about.
  17. M

    Rotational Kinetic energy in a loop

    The marble rolls down a track and around a loop-the-loop of radius R. The marble has mass m and radius r (see picture). What minimum height h must the track have for the marble to make it around the loop-the-loop without falling off? This is driving me nuts. I know that the total mechanical...
  18. M

    Torque change of a rod with unequal masses

    Ah, yes. I multiplied 1/3rps by 2*pi and everything worked. Thank you!
  19. M

    Torque change of a rod with unequal masses

    It doesn't seem to work... I took 1*(2/3)^2 + 2*(1/3)^2 and got (2/3). Then I multiplied -0.1333 by (2/3) (angular acceleration times I) and got 0.0888, which is still wrong.
  20. M

    Torque change of a rod with unequal masses

    A 1.0 kg ball and a 2.0 kg ball are connected by a 1.0-m-long rigid, massless rod. The rod is rotating cw about its center of mass at 20 rpm. What torque will bring the balls to a halt in 5.0 s? I used (m1x1+m2x2)/(m1+m2) to solve for the center of mass (2/3 meters from the 1kg weight). Then I...
  21. M

    Ratio of net gravitational pull on moon

    Thanks! I was able to solve the problem!
  22. M

    Ratio of net gravitational pull on moon

    [SOLVED] Ratio of net gravitational pull on moon A new moon is almost exactly in line between the earth and the sun. A full moon is on the opposite side of the earth from the sun. What is the ratio of the net gravitational force on the moon when it is new to when it is full? I tried...
  23. M

    Momentum of bullet fired into target

    Got it! Thank you very much for your help.
  24. M

    Momentum of bullet fired into target

    The final velocity of the target is zero, right? Or is "final velocity" defined as the velocity of the target when the bullet leaves it? Is the final velocity of the target 6.9/250kg = 0.276m/s? I guess my real question is what do I need to plug in for m, v_f, and v_i in the equation I stated...
  25. M

    Momentum of bullet fired into target

    I hadn't. Now I tried some more things. Since P = mv, I calculated the initial momentum of the bullet to be 0.023*1100=25.3, and the final momentum of the bullet to be 0.023*800 = 18.4. Does that mean the bullet lost 6.9 whatevers (kg*m/s?) of momentum to the target? Does 6.9 = (mass of bullet +...
  26. M

    Momentum of bullet fired into target

    [SOLVED] Momentum of bullet fired into target In a ballistics test, a 23.0 g bullet traveling horizontally at 1100 m/s goes through a 40.0 cm-thick 250 kg stationary target and emerges with a speed of 800 m/s. The target is free to slide on a smooth horizontal surface. What average force does...
  27. M

    Preventing a box from sliding.

    1. A person driving a truck has a box in the back. They are driving at a constant speed (v_0) when they notice a red light and have to stop. What is the maximum acceleration the truck can have without causing the box to slide forward? (Answer must be given in terms of variables, as no values are...
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