# Search results

1. ### Power of the sun

Thank you! :)
2. ### Power of the sun

Homework Statement I'm carrying out a lab to investigate the power of the sun. I'm supposed to compare the light intensity of a 100W light bulb with the light intensity from the sun, by comparing the radiating heat on my cheeks (one cheek pointing to the sun, the other to the bulb). I found...
3. ### Magnetic force of a proton

Homework Statement A proton with the speed 3.7*10^6 m/s is moving in a magnetic field, parallel to the field. The magnetic B-force is 0.45T. a)Draw a figure that shows the proton in the magnetic field. Indicate the direction of the proton's velocity, the direction of the magnetic field and...
4. ### Magnetic field strength between two wires homework

Thanks so much for your help!
5. ### Magnetic field strength between two wires homework

For points to the left of the current going vertically upward, the field is anticlockwise according to the right hand rule. Vertically downward gives clockwise direction.. So for b) when the point is closer to the wire with current going anticlockwise, B will be going out of the paper (point)...
6. ### Magnetic field strength between two wires homework

Oh of course, it's 0.06m which gives B=25μT. For a) this would make 50μT (25+25) in the point (with B pointing in which direction? since each field goes its own direction after having left the middle..) b) it would make 12.5μT from the left (12cm away from the wire as specified), and 6.25...
7. ### Magnetic field strength between two wires homework

Thank you :-) I drew a picture like you said and I also drew the arrows of the magnetic field according to the right hand rule. Now I realised that the field arrows coming from each wire points in the same direction once they reach the area in the exact middle of the wire (the area where the...
8. ### Magnetic field strength between two wires homework

The numbers I used where the current I=7.5A and the radius from each wire r=0.12m and then the constant k=2*10^-7. Giving: B=kI/r => B = (7.5*2*10^-7)/0.12=1.25*10^-5 T..? Is this incorrect? The direction for the left wire (current going upwards) is anticlockwise, and for the right it is...
9. ### Magnetic field strength between two wires homework

But if the location of the point isn't specified, do I just assume that the two magnetic fields affect the point equally? That is, assuming that the point is in the exact middle of the two wires. That would essentially give me a magnetic field of 0 T for question a)? And in b), the correct...
10. ### Magnetic field strength between two wires homework

Homework Statement Two straight parallel wires are placed vertically on a wall. The distance between the wires is 12 cm and the current through each one is 7.5A. In the left wire the current is directed upwards and in the right one the current points downwards. Determine the magnetic field...
11. ### Coulomb's law

Oh, I see! Thanks :)
12. ### Coulomb's law

Oh, you mean for every action there is an equal and opposite reaction? So if q2 works on q1 by 55μN, this means that q1 works on q2 by 55μN? So then in b) I just add them together to make 110μN, which I then plug into coulomb's law: 110 μN = (k*q1*q2)/d^2 And solve for d?
13. ### Coulomb's law

Homework Statement Two small charges q1 = +2.65 nC and q2=-4.75nC are at a certain distance from each other. Q1 is affected by a force of 55μN from q2. a) how large is the force on q2? Draw a figure that shows the electric forces that work on q1 and q2. b) determine the distance between the...
14. ### Forces on a painting

Thank you, that really helped! I was just wondering, does the nail exert an upward normal force on the wire (seeing as another force must help keep the wire and painting in equilibrium)? And if so, then is it, in this case, equal to the gravitational force since it must be perpendicular to the...
15. ### Forces on a painting

I realize now you meant free body diagram, so what I figured out was the following: a) The forces on the nail is the gravitational force from the wire and the painting, pointing downwards. The nail works on the wire by a normal force that is as large as the gravitational force 5.9N but in the...
16. ### Forces on a painting

Thanks stewartcs, try this link to the picture instead http://img120.imageshack.us/my.php?image=tavlan6hj0.png a) What's an FBD? So I should just disregard the phrasing and assume they mean that I should find the force ON the nail? So then I just set F=mg=0.6*9.82=5.9N? And then do the same...
17. ### Forces on a painting

Homework Statement This question comes from a lab that we did a while ago: Hang a painting on a nail by a thread. The weight of the painting was 0.4 kg. a) Calculate the force in the nail that holds up the painting. b) Calculate the forces that work on the thread holding the painting in...
18. ### Bouncing balls

Thank you so much alphysicist! I realized the mass is 0.0985kg, giving an impulse of 1.08 kgm/s. Also for c) I'd say now it's rather obvious that the second alternative is the correct one, since vfinal = 5.149 m/s and vinitial=5.863m/s, giving \Delta v=11.01m/s, and the acceleration must be...
19. ### Bouncing balls

Homework Statement A ball is dropped from a height of 1.75m. It bounces on the floor and reaches a maximum height of 1.35m above the floor. The ball's weight is 98.5g. a) What is the ball's velocity just before and just after the bounce? b) How large is the impulse that the ball gets in the...
20. ### Colliding car

Hello, I've tried solving the following question: A car collides with a tree with a velocity of 75km/h. The car was compressed 1.1m after the collission and the car's mass is 1100kg (including the driver), and the driver's mass is 71kg. a) What is the kinetic energy just before the...
21. ### Friction constant

Oh, I used the wrong velocity! So now I did it with Lisa sitting 1.2m from the centre, v=s/t=2πr/T giving v = 1.88m/s. Plugging into v^2/rg= μ=0.3..?
22. ### Friction constant

Thanks for helping out! Is the assumption wrong? So then I should calculate the normal&gravitational force and then split the centripetal force between them? How would you do that?
23. ### Friction constant

Hey, i'm having trouble finding the friction constant in the following question: Lisa is sitting on a carousel 0.55m from the centre. The carousel rotates at 15laps/min and Lisa weighs 33kg. a) what is Lisa's velocity? b) Lisa moves away from her spot so that she is rotating 1.2m from the...