# Search results

1. ### Finding length and longitudinal magnification

Homework Statement A small object of length dL is placed on the axis of a converging mirror of focal length f. The center of the object is a distance o from the mirror. Determine the length of the image and thus effective determine a longitudinal m' = dL'/dL for the lens. Homework...
2. ### Glasses to fix near points and far points

Homework Statement a)A person has a near point of .6m and far point of 2m . What power of glasses would be needed for the person to see infinitely far away. Assume that glasses are 2cm from the person's eyes. If the person used those glasses, what would his new near point be? b) What...
3. ### Mixing ice, steam, and water and find equilibrium

Homework Statement .15 kg of steam at 100 degree Celcius is mixed with .2kg of water at 50 degree and .2 kg of ice at 0 degree. Determine the final temperature and phase(s) of the final state. Assume that no energy is lost to the surroundings. Homework Equations The Attempt at a...
4. ### Roof withstanding a storm

Homework Statement Someone is putting a small shed in their backyard. The roof is not nailed down so gravity alone is holding it down. The wind suddenly flows across the top of the roogf at 20 m/s. The air inside the shed is 1.01 x 10^15 Pa, the normal atmospheric pressure. The roof has an...
5. ### Density and simple harmonic motion

Homework Statement A mass of density d floats in a liquid of density d_L. The mass is then pushed down a distance x and let go. Use Newton's Second Law to demonstrate that the mass will undergo simple harmonic motion. Recall that the SHM equation is d^2x/dt^2 + w^2*x = 0. Assume there is...
6. ### Releasing a sphere from water

Homework Statement A 1kg hollow sphere of volume .00419m^3 is released from rest at the bottom of a 2m deep pool of water (density of water is 1000kg/m^3). The sphere accelerates upwards and flies out of the pool. How high does it get above the pool before coming down. Ignore the brief time...
7. ### Fluid displacement

Homework Statement A small child floats in a boat in a swimming pool. The boat contains an anchor The child drops the metal anchor into the water and watches it sink to the bottom. Meanwhile, the water level in the pool (measured by its height on the side of the pool) actually drops. Why...
8. ### Drawing free body diagrams for pendulum

Homework Statement I have to do this for a lab. Draw and label the free body diaggram of a pendulum when it is at its maximum amplitude of 30 degrees. The magnitudes of the vectors must be correctly scaled and the directions correct. Homework Equations The Attempt at a Solution...
9. ### More static problems

I have no idea on how to start these two problems. I haven't done any work, but please give me some hints on how to get started. The two problems are here http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1461065539 For problem 14, the anskwer are...
10. ### Find angular velocity

The problem is problem 6 at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1460003525 A long thin rod of mass M and length L with two balls of mass M1 (same mass for both) attached is allowed to rotate about the horizontal axis shown. The bar is...
11. ### Find forces in ladder

Each side of a stepladder is 8m long and there is a hinge at the top. An 87kg man is 6m up one side and there is a 2.5m long rope connecting the two sides. The rope is exactly halfway up the ladder. Assume that the floor is frictionless and neglect the weight of the ladder. Find the tension...
12. ### Find minimum force to raise wheel

What minimum force F applied horizontally at the axle of the wheel is necessary to raise the wheel of mass M and radius R over a step of height H. A picture for this is at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1460005538 The answer...
13. ### Find minimum force to tip block

A force F applied at point A is just large enough to tip over a block of mass M. The block will rotate about its bottom right corner. Find the magnitude of F. The picture for this is problem 13 at this link...
14. ### Find the tension with using forces and torques

A traffic light hangs from a structure shown at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1460004546 The uniform aluminum pole has a mass of 8 kg and is 7.5m long. The traffice light has a mass of 5kg. The cables are massless. Cable 1 is...
15. ### Static equilibrium and a ladder

A ladder leans against a frictionlee wall. If the bottom of the ladder is pushed closer to the wall (so theta increases) which of the following change? Why or why not? Assume the ladder is in static equilibrium. a) Normal force exerted by the ground b) Normal force exerted by the wall...
16. ### Find angular velocity using angular momentum

A 20kg girl stands on a large turntable 4m from its center. The turntable has a moment of inertia (about its roation axis) of 200kgm^2. Assume that the girl is a point mass. a) Assume that the girl and turntable are rotating at 1 rad/s. If the girl walks inwards to a radius of 3m and...
17. ### Angular momentum

A 2kg object has a position vector r = -4t i + 3t^2 j (m). Find its angular momentum relative to the origin as a function of time. The correct answer is -24t^2 k (kgm^2/s). I know that L = r*p and p is mv so I differentiate r to get v v = -4 i + 6t j do I just multiply 2 and the...
18. ### Find axis to minimize moment of inertia

Two masses (M1 and M2) are connected by a thin massless rod of length L. a) Determine the location of an axis perpendicular to the rod) which minimizes the moment of inertia of the system. The answer is "with M1 at the origin x = M2*L/(M1+M2) I know that I = Sum of ( M1*r1^2)...
19. ### Another yoyo question

A yoyo is allowed to drop freely with a string held fixed in place at the top. Assume that the yoyo is a uniform disk of mass M and radius R. 1) Use Newton's Second Law to find the linear acceleration of the yoyo and the tension in the rope. My answer key says that the answers are 2/3 g...
20. ### Motion involving both translation and rotation

Hello everyone. Thanks for all the help today. I know I have asked a lot of questions. This is my last one today. A spherical billard ball is sliding with a speed v_o. It has a radius R, mass M, and there is a friction coefficient mu. Determine the distance the ball travels before it...
21. ### Conservation of rotational energy

A cylindrical can of paint with (I = .5MR^2) starts from rest and rolls down a roof as shown in the link http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1424481748 Determine how far the can lands from the edge of the house. This is my work, but I...
22. ### Yo-yo question

I have the question at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1423959807 I have to determine what happens if each force is applied. This is what I think. If force one is applied, the yoyo will rotate clockwise, and friction will push it...
23. ### Another problem with pulleys

Two masses are connected as shown at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1423595691 It is problem 15 I drew my free body diagrams, but I can't figure out the relationship to write for the pulley since the incline is frictionless. I know...
24. ### Finding velocity taking the pulley into consideration

The picture for this problem is at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=128765607&imageID=1423590496 It is problem number 9. I also have my work so far there. Two blocks are connected as shown. Friction between M1 and the horizontal surface is...
25. ### Finding torque (vector cross product)

A particle position is described by position vector r = 3i + 2j and the force vector i - 2j acts on the object. 1) Find the torque about an axis through the origin and perpendicular to the xy plane. Draw the two vectors to check your torque direction. I used the right hand rule and found...
26. ### Rotational motion of a ball

These problems have diagrams with them so I posted those pictures are at http://viewmorepics.myspace.com/index.cfm?fuseaction=viewImage&friendID=21023924&imageID=1420239256 1) A spherical ball rolls up an incline. Determine the acceleration of the ball and the magnitude and direction of...
27. ### Application of Taylor Series

The electric potential V at a distance R along the axis perpendicular to the center of a charged disc with radius a and constant charge density d is give by V = 2pi*d*(SQRT(R^2 +a^2) - R) Show that for large R V = pi*a^2*d / R This is what I have done so far... V = 2pi*d *...
28. ### Center of mass

A 50 kg person at the left end of a 75kg boat is 6 m from shore. The person walks to the other end of the boat 3m away. How far is the person from the shore now? The system center of mass fixed in space so as the person moves right, the boat moves left. I know that the person moves 3 m to...
29. ### Finding normal force with momentum

Water falls without splashing at a X kg/s from a height H into a bucket of mass M. The bucket sits on a sacle. Determine the reading of the sacle as a function of time. I know the the sum of all forces is equal to the derivative of momentum with respect to time. Mg is the force at time =...
30. ### Circular motion with tangential acceleration

A car is initially at rest. It starts mvoing with tangential acceleration a_tan along a flat circular track of radius r. If the coefficient of static friction is mu, determine the total distance traveled by the car before it skids off the track. This is what I did. I drew the free body...