Physics Answers

A top is a toy that is made to spin on its pointed end by pulling on a string wrapped around the body of the top. The string has a length of 89 cm and is wrapped around the top at a place where its radius is 53.06 cm. The thickness of the string is negligible. The top is initially at rest. Someone pulls the free end of the string, thereby unwinding it and giving the top an angular acceleration of +19 rad/s^2. What is the final angular velocity of the top when the string is completely unwound?

A pitcher throws a curveball that reaches the catcher in 0.14 s. The ball curves because it is spinning at an average angular velocity of 400 rev/min (assumed constant) on its way to the catcher's mitt. What is the angular displacement of the baseball (in radians) as it travels from the pitcher to the catcher?

A space station consists of two donut-shaped living chambers, A and B, that have the radii shown in the figure. As the station rotates, an astronaut in chamber A is moved 236 m along a circular arc. How far along a circular arc is an astronaut in chamber B moved during the same time if r_a = 463 m and r_b = 493 m?

A crane has an arm length of 20 m inclined at 30deg with the vertical. It carries a container of mass of 3 ton suspended from the top end of the arm. Find the torque produced by the gravitational force on the container about the point where the arm is fixed to the crane. Given: 1 ton = 1000 kg; neglect the weight of the arm. Hint: take the force and perpendicular distance from the point where the arm is fixed to the crane.

A certain planet spins on its axis 2 a day and orbits the sun 13 a year. Determine the average angular velocity (in rad/s) of the earth as it spins on its axis.

A person is riding a bicycle, and its wheels have an angular velocity of 15.15 rad/s. Then, the brakes are applied and the bike is brought to a uniform stop. During braking, the angular displacement of each wheel is 13.47 revolutions. How much time does it take for the bike to come to rest?

A woman whose weight is 722 N is poised at the right end of a diving board with a length of 8.92 m. The board has negligible weight and is bolted down at the left end while being supported 2.79 m away by a fulcrum. Find force that the fulcrum exerts in the board.

after 2 hours the displacement of the car is 150 km north. the initial displacement of the car is 0 what is the average velocity of the car

You attach a 2.50 kg block to a horizorsal spring that is fixed at one end. You pull the block until the spring is stretched by

0.400 m and release it from rest. Assume the block sides on a horizontal surface with negligible friction The block reaches a

speed of zero again 0.400 s after release (for the first time after release). What is the maximum speed of the block (in m/s)?

prove that velocity of light is 3×10^8 ?