Modern Physics

8. Imagine for a minute that the moon is held in its orbit about the Earth by electrical forces rather than by gravitation. What is the necessary electrical charge -Q that would be on the Earth and +Q that would be on the moon to hold the moon in a circular orbit of 27.3 days? The Earth-moon distance is 384,000 km and the mass of the moon is 7.35 x 1022 kg.

3) Sketch and label a graph of extension (∆I) against Weight (W) including the limit of proportionality and beyond this point.

4) Show how you can work out the value of spring constant (k) from the graph.

A 0.50 kg pendulum bob is released from some initial height such that the speed of the bob at the bottom of the swing is 3.8 m/s. What is the initial height of the bob?

A spring is compressed by 0.044 m. What is the potential energy of the spring if the spring constant is 739 N/m. (an uncompressed spring has zero potential energy. Also, give your answer in joules to two decimal places)

A ball is held in place at one end of the spring as shown in the figure. The spring is initially compressed by 0.026 m and the released. When the spring reaches its relaxed (uncompressed) position, all of its potential energy is transferred to the ball's kinetic energy. What is the ball's kinetic energy at that instant if the spring constant is k = 277 N/m.

What is the power required for the winch on a rescue helicopter to lift two people a distance of 25.6 m in 111.2 s? The person being rescued is 79.3 kg, and the rescuer is 90.5 kg.

The figure shows a spring in its equilibrium position at x = 0. The spring can then be stretched, x > 0; or it can be compressed, x < 0. The minimum value of the elastic potential energy stored by the spring is Group of answer choices when the spring is at its equilibrium position and x is zero. when the spring is a a maximum compression and x is negative. when the spring is at a maximum stretch and x is positive.

Two identical balls are thrown directly upward, ball A at speed vand ball Bat speed 2 v, and they feel no air resistance. Which statement about these balls is correct?

The figure shows a block attached to a spring. The spring is initially in its equilibrium position (Not stretched or compressed). If the block is pulled to the right and then released, the block's kinetic energy will be at its maximum