A uniform door of mass 22.5 kg, length 2.10 m, and width 0.900 m is kept in a vertical position by frictionless hinges on its length. A 135 g dove strikes the door at a point three-quarters of the width measured from the hinges with a horizontal speed of 20.0 m/s. The dove bounces off with a speed of 8.00 m/s in the opposite direction. State why angular momentum is a conserved quantity while linear momentum is not based on this collision.
A uniform window that is 0.700 m long and 0.500 m wide has a mass of 11.0 kg. The window is pivoted by frictionless hinges along its width and allowed to hang vertically. A 0.850 kg unlucky peregrine falcon has a level flight speed of 100 km/h when it hit the window at its center. The falcon bounces back at a speed of 60 km/h. Calculate the window's angular speed immediately after its hit by the unlucky falcon.
A uniform board of mass 22.5 kg, length 2.10 m, and width 0.900 m is kept in a vertical position by frictionless hinges on its length. The board is unlatched and at rest when a kid strikes the board's center with a lump of their sticky molding plasticine of mass 450 g. The plasticine hits the board with a level speed of 12.0 m/s and is perpendicular to its surface. i) Determine the board's angular speed after collision. ii) Will the plasticine significantly contribute to the system's moment of inertia after the collision?
If planets orbit a central star too slowly, they will be attracted by gravity and fall into the star. Suppose a planet moves radially (not orbiting the sun or spinning on its axis) from its orbit and is embedded into the sun's equator. Taking the mass of the sun to be M, what is the mass of the planet in terms of M that increases the sun's average period of 27 days by 10%? You may find it useful to assume that the planet is far much smaller than the sun and that the sun is consistent at all points.