Types of Forces Gravitational Force Vector, Weight, and Mass Net Force Newton’s Laws Ropes and Pulleys Applying Newton’s Laws Friction Force Applications of the Friction Force What We Have Learned/Exam Study Guide Multiple-Choice Questions/Questions/Problems Friction 1. A physics major is cooking breakfast when he notices that the frictional force between his steel spatula and his Teflon frying pan is only N. Knowing the coefficient of kinetic friction between the two materials, he quickly calculates the normal force. What is it? 2 Starting from rest, one sled can reach a speed of m/s in s and can be brought to a stop again in s. a. Calculate the acceleration of the sled when starting, and compare it to the magnitude of the acceleration due to gravity, m/s2. v2 v1 v a t t m/s m/s s
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With the recent publication of PHYSICS IS there are now three Ask the Physicist books! Click on the book images below for information on the content of the books and for information on ordering. QUESTION: I am constructing a floating dock out of pressure-treated lumber and gallon empty plastic barrels and want to ensure that I provide sufficient buoyancy. Although the dock comprises a ramp and a platform, they will be only loosely connected with slack rope and eye boltsand the buoyancy calculations for the platform are easy; it's the ramp that is giving me headaches.
Specifically, one end of the ramp will be sitting on the shore and the other end will be supported by the plastic barrels. The ramp is T-shaped, with the lakeside end wider to accommodate the barrels. Although I've meant for this question to be somewhat general to allow for design modifications, I will mention that I've built part of the ramp already, with the walkway being 3' wide and 8' long, and the cross of the T being 5' wide and 3' long and covering two empty barrels; I'm willing to add another section with more barrels if needed.
Any help in analyzing buoyancy of a T-shaped ramp with the narrow end resting on land would be greatly appreciated! ANSWER: I will not be able to do any quantitative calculations without knowing the weights of the ramp and dock. Also, will the level of the water remain fairly constant? FOLLOWUP :. I must mention that I modified the design to make the walkway eight feet longer, so that it is now 16 feet long, physics 247 homework help friction weight.
Also, I had another empty gallon barrel on hand, and placed it lengthwise under the walkway at the end where the walkway joins the cross of the tee.
The salient data for the components are as follows:. T-shaped ramp total weight lb. Walkway lb is 3 feet wide and 16 feet long; a gallon drum is placed under the walkway on the lake end. Cross of tee lb : 5 feet wide and 3 feet long, covering two gallon drums. The dock platform weighs lb and is 8'x8'. Four gallon drums support it. My dock will be located in a tributary of the Potomac River.
As such, the water is tidal, varying in depth between 2 and 5 feet. This is the reason I did not join the ramp and the platform rigidly, as I anticipate that the angle of surface of the ramp relative to that of the platform will fluctuate, given that one end of the ramp rests on the shore.
In order to help visualize the situation, I am attaching three JPG images which I created in Sketchup. Please note that these images do not include the latest modification, whereby I lengthened the walkway and placed a barrel under its far end.
Also, I recognize that you will probably make certain simplifications in order to expedite the analysis, physics 247 homework help friction weight. That is fine with me; I only wish to obtain a rough idea of the limits of motion of the ramp and dock as I walk upon them.
At high tide the walkway and platform are approximately horizontal. At low tide the water level is about feet down. I will first do the platform which is easiest if you assume that the load is at the center. I made an estimate of how much the platform would tilt if the load were moved over to 1 ft from one side edge. Without going into details, the heavy side would go down by about 2. the weight of the tee and two barrels under it as well as the net buoyant force of those barrels act at the weight and buoyant force of the third barrel act at the maximum weight W acts at a distance x from the shore.
there is a force F exerted up by the shore which we will not need to know. Physics 247 homework help friction weight have assumed that the ramp has no interaction with the platform, since reference is made to "slack ropes". All this is shown in my diagram. If one now sums the torques about the point of shore contact and sets that sum equal to zero, the product Wx can be solved for.
I am guessing that this result does not make you happy! I am not sure how rigidly coupled the platform and walkway are "slack ropes"but suppose that they are coupled as if, when horizontal, they were rigidly attached.
It would seem that it is important that the coupling be designed such that the platform can help hold up the walkway. I figure that the walkway will only go down a maximum of about 15 0 at low tide; this should not physics 247 homework help friction weight alter the estimates I made for the horizontal situation. So you should allow a fairly rigid coupling like some kind of hinge.
QUESTION: If you have two metal spheres of the exact same volume, however with differing masses, say one sphere at 1kg and one at 10kg, attached each to an identical parachute, will they fall at different speeds? We know that two spheres of the same volume with differing mass will fall at a nearly identical speed, as the drag is identical. I have had it put forward to me that somehow adding a parachute into the system dramatically affects the outcome.
ANSWER: "We know that two spheres of the same volume with differing mass will fall at a nearly identical speed …" Sorry, that statement is wrong. It is true, as you state, that, since they have the same size and shape, the drag forces will be the same on both.
But, that force will have a much bigger physics 247 homework help friction weight on the less massive sphere because it has much smaller inertia. You can understand this intuitively. Imagine a bowling ball and a balloon the same size. Drop them from a height of 2 m and surely the bowling ball will hit the floor first. As the object falls from rest, v gets bigger and bigger.
QUESTION: I have a 40' ladder that weighs pounds. Standing it up with it's foot against a wall. And walking it up. It gets heaverier and heavier; at the half way point it feels the heaviest. How much does it weigh half way stood up? ANSWER: The weight of the ladder does not change if you go up it. It is always lb, physics 247 homework help friction weight. Why do you think it gets heavier? FOLLOWUP QUESTION: With the feet of the ladder against the wall.
with ladder not extended each section is like. Starting at the inter end of the ladder. standing it up you have to go ring by ring it just feels like it weighs a ton before it is stood all the way up. feels heaviest at a degree angle. it takes all you can do to stand it up. ANSWER: There are four forces acting on the ladder: the weight W of the ladder, the force F which you apply, the force N which the floor exerts physics 247 homework help friction weight, and the force f which the wall exerts to hold the ladder from sliding.
I have assumed that F is applied perpendicular to the ladder. So, we have to make a further assumption about how the ladder is lifted, physics 247 homework help friction weight. Having done this, my recollection is that I start off lifting the end straight up over my head and then raise it by walking toward the physics 247 homework help friction weight lifting as I go. For the rest of the way F decreases rapidly to zero when the ladder is upright.
The angle for the maximum F is about 35 0also about what you observed, physics 247 homework help friction weight. ADDED COMMENT: To determine in general the location of the maximum value of Fset its derivative equal to zero and solve for D. QUESTION: If a wheel is rolling without slipping on an inclined plane, friction force is the one that provides the torque, why does the torque provided by friction increase as the angle of the inclined plane is increased yet the friction force decreases as the angle of inclination is increased?
ANSWER: You are wrong about how f changes with θ. This problem has three unknowns, so you must generate three equations:. You can see that f increases with θ. QUESTION: Glad I found your site, my name is Ben, and this question is something I'm working on professionally, not homework. I use Autodesk Inventor's Dynamic Simulation to model collisions and some of the results for a specific simulation don't seem consistent. So, a colleague suggested we simplify the problem and work the numbers out by hand, but we can't figure it out.
Here is a diagram:. A rod blue of length 2m and mass of 1kg can freely pivot about it's center orange dot which is connected to a frictionless track purple running in the Y direction.
Collision is perfectly elastic, friction is zero. How can I determine the final velocity of the rod along the track, and what is it's rotational speed? And more importantly, I need to know what effect the rod angle has on these two answers, physics 247 homework help friction weight.
Then I can solve and plot a chart for all angles from 0 to 90 and compare with my Inventor results. I'm really having trouble with the moment of inertia part, being that it's not struck in the center, physics 247 homework help friction weight, or the end.
ANSWER: There are important errors with the problem as you state it. The first obvious error in this problem is that the direction and magnitude of the final velocity of the ball is impossible, physics 247 homework help friction weight. If the ball carries off physics 247 homework help friction weight the energy it came in with, the rod must end up with no energy. And, the angular momentum relative to the COM of the incoming ball is equal and opposite that of the outgoing ball, physics 247 homework help friction weight, so the rod would have to be rotating to conserve angular momentum.
So I thought to simply redraw the picture but with the final ball velocity having unknown components 2 unknowns. Two other unknowns are the final speed of the COM and the angular velocity of the rod about the COM.
However, I only can see three equations: conservation of energy, linear momentum only yand angular momentum. I am still pondering the question, but there is too little information or I am missing something.
WCLN - Physics - Friction Forces
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Friction 1. A physics major is cooking breakfast when he notices that the frictional force between his steel spatula and his Teflon frying pan is only N. Knowing the coefficient of kinetic friction between the two materials, he quickly calculates the normal force. What is it? 2 We value excellent academic writing and strive to provide outstanding essay writing service each and every time you place an order. We write essays, research papers, term papers, course works, reviews, theses and more, so our primary mission is to help you succeed academically Starting from rest, one sled can reach a speed of m/s in s and can be brought to a stop again in s. a. Calculate the acceleration of the sled when starting, and compare it to the magnitude of the acceleration due to gravity, m/s2. v2 v1 v a t t m/s m/s s
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