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Questions11
• ### Help on Practice Physics Final Exam?

Express, as a function of τ, the time interval needed for the amplitude of an oscillation to reduce to half of its initial value.

I can't solve this problem, and the TA's can't either. Tried contacting the Prof., but he's not responding at all. Could someone help me through this question? This is all the information given to us.

Physics8 months ago
• ### Help on Practice Exam Challenge question?

If a person is 16 % shorter than average, what is the ratio of his walking pace (that is, the frequency f of his motion) to the walking pace of a person of average height? Assume that a person's leg swings like a pendulum and that the angular amplitude of everybody's stride is about the same.

Could I get some help on how to come up with the answer please? Thanks for those who take their time to explain through the problem.

Physics8 months ago
• ### Help on Physics Practice Exam?

Express, as a function of τ, the time interval needed for the amplitude of an oscillation to reduce to half of its initial value.

This question has been asked before on reddit, but it was never answered in terms of tau. What's funny is that the reddit user had the exact same professor and I, and both he and I couldn't get proper help from our TA's. What's funny is that they keep messing up on the problem and saying they "weren't sure" whether they were right or not. I tried e-mailing the prof., but he's not responding. Probably because he's busy with his "rEsEaRcH." Sorry for the rambling. If anyone can help me out, I'd greatly appreciate it.

Thanks

• ### Ratio of walking pace?

If a person is 16 % shorter than average, what is the ratio of his walking pace (that is, the frequency f of his motion) to the walking pace of a person of average height? Assume that a person's leg swings like a pendulum and that the angular amplitude of everybody's stride is about the same.

• ### What minimum value for the coefficient of static friction μs between B and C (no slip). Ignore any friction between B and horizontal surface?

Block B in (Figure 1) is free to slide on the horizontal surface. With block C placed on top of B, the system undergoes simple harmonic motion with an amplitude of 0.12 m . Block B has a speed of 0.22 m/s at a displacement of 0.080 m from its equilibrium position.

Can someone help me with the process of getting the answer? I was able to come up with w=2.46 and the period being T=2.55 seconds. I just can't solve the second part of this problem.

• ### If you assume that the motion will be simple harmonic motion, how long will a one-way trip take?

You get a crazy idea to dig a tunnel through Earth from Boston to Paris, a surface distance of 5850 km, and run a passenger train between the two cities in the figure. The train would move down the first part of the tunnel under the pull of gravity and then coast upward against gravity.  Could someone explain how to get to the answer for this challenge problem I have on my practice exam? Thanks!

• ### Ignoring Earth's rotation how much energy is needed to get the same object into orbit at height h?

Ignoring Earth's rotation, how much energy is needed to get the same object into orbit at height h?

Express your answer in terms of some or all of the variables h, mass of the object m, mass of Earth mE, its radius RE, and gravitational constant G.

I got the first part of this to be

Ei = (GmmEh)/RE(RE+h)

for the energy needed to launch an object from the surface of Earth to a height h above the surface.

Any help is greatly appreciated

• ### Help? Two particles, each of mass m, are initially at rest very far apart.?

Obtain an expression for their relative speed of approach at any instant as a function of their separation distance d if the only interaction is their gravitational attraction to each other.

Express your answer in terms of some or all of the variables m, d, and gravitational constant G.

Any help is greatly appreciated! Thanks!

• ### What is the max upward force you can exert so that the ball doesn't rotate? Assume a uniform distribution of inertia.?

A 4.3-kg bowling ball is perched on a concrete ledge directly below your dorm room window, with the side of the ball opposite the holes touching the wall. Wanting to hold the ball in place so that it doesn't roll off and land on somebody, you manage to hook one of the holes with a wire and exert a purely tangential (and vertical) force on the ball. The coefficient of static friction between ball and ledge is the same as that between ball and wall, μs = 0.42

Physics9 months ago
• ### What is the max upward force you can exert on the ball so that the ball does not rotate? Assume uniform distribution of mass.?

A 4.9 kg bowling ball is perched on a concrete ledge directly below your dorm room

window, with the side of the ball opposite the holes touching the wall. Wanting to hold the

ball in place so it doesn’t roll off and land on somebody, you manage to hook one of the

holes with a wire and exert a purely tangential (and vertical) force on the ball. The

coefficient of static friction between the ball and the ledge is the same as that between the

ball and the wall, µs = 0.51.

Any help please? I'd like to know HOW to solve this, please. Thanks!

Physics9 months ago
• ### How long does it take to come to rest? And How much work has to be done on the turntable to bring it to rest?

A record player turntable initially rotating at 33 1/3 rev/min is braked to a stop at a constant rotational acceleration. The turntable has a rotational inertia of 0.021 kg⋅m^2 . When it is switched off, it slows down to 75% of its initial rotational speed in 5.5 s

Any help with this is greatly appreciated! I'd like to know the thought process so I can better understand what's happening, too, please. Thank you!