A910-kg object is released from rest at an altitude of 1200 km above the north pole of the earth. if we ignore atmospheric friction, with what speed does the object strike the surface of the earth? (g = 6.67 × 10-11 n · m2/kg2, mearth = 5.97 × 1024 kg, the polar radius of the earth is 6357 km)

Acentrifuge in a medical laboratory rotates at an angular speed of 3,700 rev/min. when switched off, it rotates through 54.0 revolutions before coming to rest. find the constant angular acceleration (in rad/s2) of the centrifuge. your response is within 10% of the correct value. this may be due to roundoff error, or you could have a mistake in your calculation. carry out all intermediate results to at least four-digit accuracy to minimize roundoff error. rad/s2

Ideal meters problem. what internal resistance is ideal for a voltmeter? what internal resistance is ideal for an ammeter?

Atrain is traveling at 30.0 m/s relative to the ground in still air. the frequency of the note emitted by the train whistle is 262 hz. the speed of sound in air should be taken as 344 m/s. what frequency (f approach) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and approaching it? what frequency (f recede) is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction opposite to the first train and receding from it?