1. avito009

    Why does the moon not fall into the Earth?

    I know that the gravitational pull of the Earth on the moon makes moon orbit the Earth. But the reason why moon does not fall off in a straight line towards the Earth is that the moon has orbital angular momentum. But how does the moon having orbital angular momentum prevent it from falling...
  2. J

    A practical method to turn the planet Earth. Is there a physics level flaw in this?

    Studying the Earth-Moon tidal force it occurred that energy from the system (moon) could be used to apply an external force (non-Earth reference frame) to turn the Earth. By affixing a horizontal lever (eg. 100m long) onto the ocean floor or an island mass, and attaching a large plate...
  3. H

    How can the magnitude of the gravitational forces of the earth and moon be equal?

    I know the equation for the force of gravity = GMm/(r^2). However, when I set mg = GMm/(r^2) and Mg = GMm/(r^2), I feel that there is an error in the logic. For instance, say that the force of gravity is = 10000N and if we set mg = 10000( the different mass and gravity for the moon) and if we...
  4. V

    Shooting the Moon

    We have given coordinates on the Earth from where we are shooting to the Moon (bullet has really small mass). The Moon orbit and therefore Moon position in time t is known. The task is to compute the initial velocity vector (the angle and velocity of the bullet), so the bullet will reach the...
  5. N

    Moon orbit

    Why does the Moon stay in its orbit without either leaving or approaching the Earth (more than it does)? Naturally, there is gravity and centrifugal forces counteracting one another, but why the balance? A man-made satellite may need occasional speed adjustment. Is there a balancing force...
  6. B

    Electrostatic/charges on earth & moon

    Hi, first post. I need help for this question: How much equal charge would be needed on the earth and on the moon for the electrostatic repulsion to balance the gravitational attraction? I'm not sure where to start; I know that F = (kq^2)/r^2 and FG = (Gmemm)/r^2 so do I set them equal to each...
  7. K

    why star is luminous object while moon is non-luminous??

    same as title, many thanks!
  8. C

    Kepler (conservation of angular momentum) and the moon,

    Hi, The moon is receding at about 4cm/year. Apparently because it is speeding up. Does the moon's orbit then violate Kepler's law of planetary motion? How can the integral remain equal for sweeps of the moons orbit if the moon is moving away. Is this an example of Kepler's law being...
  9. I

    image of the moon

    Formulas are \frac{1}{f}=\frac{1}{di}+\frac{1}{do} \frac{hi}{ho}=\frac{-di}{do} F stands for focal point, di is distance to the image, do is distance to the object, hi is height of the image and ho is height of the object. \frac{4.5*10^-5}{3500}=\frac{-di}{380000} f=-4.88*10^-3...
  10. T

    Apollo 14 Golf on Moon (Projectile Motion)

    During the Apollo 14 mission, American astronaut Alan Shepard hit a golf ball. Given that the acceleration due to gravity on the moon's surface is 1.62 m/s^2, assuming that the angle of the shot was 20 degrees above the surface, and that the ball traveled 350 m, calculate the initial velocity of...