Homework Help: Solve Physics & Math Problems with Answers

  • Thread starter Thread starter Stephanie
  • Start date Start date
  • Tags Tags
    Homework
AI Thread Summary
The discussion focuses on solving various physics problems involving motion, energy, and forces. Key topics include determining the minimum height for an object to remain on a track in a loop, calculating work done by air resistance on a falling paratrooper, and analyzing the mechanics of a long jump. Additional problems involve the speed of a ball on a pendulum and energy transfer from water flowing over a dam. Participants are encouraged to specify where they are struggling for more targeted assistance.
Stephanie
Messages
3
Reaction score
0
I've tried these problems but I need some help.

44. a small mass m slides without fritction around the looped apparatus show in the picture below. If the object is to remain on the track, even at the top of the circle (whose radius is r), from what minimum height H must it be released?

http://i75.photobucket.com/albums/i319/Thepalaceguild/draw.jpg

71. A paratrooper fell 370m after jumping from an aircraft without his parachute opening. He landed in a snowback, creating a crater 1.1m deep, but survived with only minor injuries. Assuming the paratroopers mass was 80kg and his terminal velocity was 30m/s, estimate the work done on him by air resistance as he fell.

74. In a film of Jesse Owens's famous long jump in the 1936 Olympics, it is observed that his center of mass rose 1.1m from launch point to the top of the arc. What minimum speed did he need at launch if he was also noted to be traveling at 6.5m/s at the top of the arc?

76. A ball is attached to a horizontal cord of length L, whose other end is fixed, (picture below). (a) If the ball is released, what will be its speed at the lowest point of its path?(b)A peg is located a distance H directly below the point of attachment of the cord. If H=.8L, what will be the speed of the ball when it reaches the top of its circular path about the peg?

http://i75.photobucket.com/albums/i319/Thepalaceguild/draw2.jpg

81. Water flows over a dam at the rate of 550 Kg/s and falls vertically 80m before striking the turbine blades. Calculate: the rate at which mechanical energy is transferred to the turbine blades, assuming 60% efficiency.

85. A 75Kg student runs at 5.0 m/s, grabs a rope, and swings out over a lake. He releases the rope when is velocity is zero. (a) What is the angle (-)(theta) when he releases the rope? (b) What is the tension in the rope just before he releases it? (c) What is the maximum tention in the rope?


Thanks to all who respond. ^_^
 
Last edited by a moderator:
Physics news on Phys.org
Stephanie said:
I've tried these problems but I need some help.

Well, if you're stuck somewhere, you could perhaps point out where the problem is.
 
44.
N + mg = mv^2 /r -at the top of the loop
N goes to zero and
mg = (mv^2)/r

so v minimum = √rg

now use energy conservation
mgh + 0 = 0.5m(√rg)^2
h = 0.5r

and your H = 2r+ h = 2.5*r
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top