# Search results

1. ### Find the reactions the pin A and roller D exert on the truss

Homework Statement The rigid truss supports the loads shown. Find the reactions the pin A and roller D exert on the truss. All concentrated loads act on the pins joining the truss members Homework Equations ƩMa= -5ft(3kips)-10ft(2kips)-.707(1kip)10ft+Dy(15ft) Dy=2.80 kips*ft The Attempt...
2. ### Emf of a battery

what are the equations you would use in this situation?
3. ### Emf of a battery

so on the larger voltage batt would i use equation Vab=Emf-Ir = 18-(.625*1) and on the batt with voltage being forced across it use Vab=Emf+... idk
4. ### Emf of a battery

Homework Statement determine the terminal voltage in each battery. Emf1=18V r1=1 ohm EMF2=12V r2=2 ohm R=6.6 ohms also the batterys currents are opposing each other. Homework Equations Vab=emf-Ir The Attempt at a Solution i used kirchnoffs rule to find the current I ...
5. ### Centripetal force prob

ok thanks, but for the second problem i meant to write: If the car is traveling along and the road is banked at 13 degrees, and there is no friction, at what velocity would the car begin to slide? If im remembering correctly it seems as though my professor broke up the mg component for this...
6. ### Centripetal force prob

Homework Statement prob1) For a car traveling with a speed v around a curve of radius r, determine a formula for the angle at which a road should be banked so that no friction is required. prob2)Calculate the frictional force needed for a 900kg car traveling around a 500m radius curve at...
7. ### Conservation of momentum prob

ok it seems like it would just be 1/3
8. ### Conservation of momentum prob

Homework Statement A wooden block is cut into two pieces, one with three times the mass of the other. A depression is made in both faces of the cut, so that a firecracker can be placed in it with the block reassembled. The reassembled block is set on a rough-surfaced table, and the fuse is...
9. ### Torque prob

Homework Statement A 7.5 m long uniform aluminum pole with a mass of 12.0 kg supports a 21.5 kg traffic light. The aluminum pole is attached to a vertical pole by a pivot near the base. A massless horizontal rope supports the aluminum pole and is connected to the vertical pole 3.80 m above...
10. ### Rotational motion

Nevermind that the speeds are the same
11. ### Rotational motion

Ok hypotenuse =4.25m and I thought the speed going up would be different than the speed going down because the hoop has an initial velocity going up.
12. ### Rotational motion

ok so i used the equation 2gyf=r^2+vi^2 solved for yf and got yf=1.1m so sin(15)=1.1/h hypotenuse=.43m im getting stuck on the last part now,solving for the time.I think i need the radius of the loop but cant seem to figure it out...
13. ### Rotational motion

oh.....that makes sense haha
14. ### Rotational motion

oh ok i forgot to put the\omega in so it should be (r\omega)2+v2=2gyf so yf=1.1m and distance up =1.7m im confused about what mode to have my calculator in? rads or degs?
15. ### Rotational dynamics prob

ok so i calculated the torque required disregarding the resistive force and got \tau=.063M/N then i calculated the torque of the resistive force and got \tau=-.006M/N so i figured i just add .006M/N of torque to .063 and got .069M/N
16. ### Rotational motion

Homework Statement A hoop rolling on a horizontal surface with a speed v=3.3m/s when it reaches a 15 deg incline.How far up the incline does it go?How long will it be on the incline before it reaches the botttom? Homework Equations I=mr2 conservation energy going up=2gyf=r2+vi2...
17. ### Moment of inertia and rotational kinetic energy

thank you:smile:
18. ### Moment of inertia and rotational kinetic energy

Homework Statement A merry-go-round has a mass of 1640 kg and a radius of 7.50 m. How much net work is required to accelerate it from rest to a rotation rate of 1.00 revolutions per 8.00s? Assume it is a solid cylinder. Homework Equations \DeltaKE=Wnet=1/2(Iw2)=14211.7J...
19. ### Rotational dynamics prob

Homework Statement A grinding wheel is a uniform cylinder of with a radius of 8.50 cm and a mass of 0.580 kg. Calculate a) its moment of inertia about its center, and b) the applied torque needed to accelerate it from rest to 1500 rpm in 5.0 s if it is known to slow down from 1500 rpm to rest...
20. ### Moment of inertia and rotational kinetic energy prob

wow i never even thought of that...thank you
21. ### Moment of inertia and rotational kinetic energy prob

Homework Statement A spool of wire mass m and radius r is unwound under a constant force F. Assuming that the spool is a uniform solid cylinder that does not slip, show that the acceleration of the center of the mass is 4F/3m Homework Equations F+f=ma f=ma-F \tau =I\alpha=Fr-fr...
22. ### Merry go round, rotational dynamics

ok that makes sense, thanx
23. ### Merry go round, rotational dynamics

well, because my lab book says "The moment of inertia is given mathematically by \Sigmamr2.... so yes it seems like the moment of inertia is mr2,however when i look at all the moment of inertias for different objects solid sphere I=2/5mr2, solid cylinder 1/2mr2 and so on.... where does the 2/5...
24. ### Merry go round, rotational dynamics

now that wouldnt be very nice:mad::biggrin: ok but i still dont know how to obtain the value of I for the kid... is it just mr2 or do i use I that is for a solid cylinder I=1/2(mr2)?
25. ### Merry go round, rotational dynamics

Homework Statement A plyground merry go round of radius r=2m had a moment of inertia of I=250kg/m2 and is rotating at 10rpm about a frictionless verticle axle.Facing the axle a 25kg child hops onto the merry go round and manages to sit down on its edge.What is the new angular speed of the...
26. ### Rotational dynamics problem

Thanx, that was perfect:biggrin:
27. ### Rotational dynamics problem

Homework Statement A uniform solid cylinder and a uniform cylindrical shell are placed side by side at the top of an incline.If they sre released from rest and roll without slipping, A)Determine their speeds when they reach the bottom B)Which objet reaches the bottom first? Homework...
28. ### Simple harmonic motion of an ideal spring

thanx for all the help...appreciatcha!:approve:
29. ### Simple harmonic motion of an ideal spring

no I mean if the mass is heavy enough(not so heavy that it deforms the spring)then it wouldn't quite rise back up to that same position..
30. ### Simple harmonic motion of an ideal spring

Ok so when you hang a mass on the spring..and then let it go.. Theoretically isn't it supposed to rise back up to the original unstretched position? I have a hard time imagining it would do exactly that depending on the mass.