<p>Hi, I'm having to write a school exam on physics 12, but I have no way of figuring out these questions since school is over and it's just exam week. If someone could help with any of these questions, you would automatically be a genius and I'd certainly appreciate it!</p>
<p>1) A 3500 kg piece of space debris is brought from an altitude of 2.1 x 10^5 m back to the earth's surface. What is the change in potential energy of this space debris? (ans= -7.0 x 10^9 J)</p>
<p>I know that the object has a potential energy of GmM/r when it is on the surface of the earth and that the potential energy when it is in space must be subtracted. I know the altitude must be added to the radius of the planet to get the radius for the formula, but I keep getting a different answer...</p>
<p>2) In an amusement park, a 2.8 m radius "drum" rotates such that a person does not fall when the "floor" drops away. If the coefficient of friction between the person and the wall is 0.35, what is the maximum period of the rotation so that a person will not fall?</p>
<p>(ans= 2.0 sec)</p>
<p>3) One method for determining masses of heavy ions involves timing their orbital period in a known magnetic ield. What is the mass of a singly charged ion that makes 7 revolutions in 1.3 x 10^3 seconds in a 4.5 x 10^-2 field?</p>
<p>(ans= 2.1 x 10^-25 kg)</p>
<p>4) A 0.10 kg metre stick forms an angle of 60 degrees with the floor. It is held up by a perpendicular force (into the sky, away from the floor) F. The bottom of the metre stick is on the verge of sliding to the right. Determine the size of the friction force being provided by the floor.</p>
<p>(ans= 0.21 N) </p>
<p>Thanks for any help on any of these questions!</p>