Posted by **Karrine** on Sunday, October 21, 2012 at 7:45pm.

I am studying for a physics exam and this is the pretest. There are some that I don't understand. If someone could help me get to the answer (show all the work so I can look it all over) that would be AMAZING! Thank you very much!

2. A roller coaster, loaded with passengers, has a mass of 2000 kg; the radius of curvature of the track at the bottom point of the dip is 24 m. If the vehicle has a speed of 18 m/s at this point, what force is exerted on the vehicle by the track? A: 4.7 x 10^4 N

5. An Object of mass 0.50 kg is transported to the surface of Planet X where the object's weight is measured to be 20 N. The radius of Planet X is 4.0 x 10^6 m. What is the mass of Planet X? A: 9.6 x 10^24 kg

6. A 3.0 rod is pivoted about its left end. A Force of 6.0 N is applied perpendicular to the rod at a distance of 1.2 m from the pivot causing a clockwise torque, and a force of 5.2 N is applied, at an angle of 30 degrees (between the rod and the force vector) at the end of the rod 3.0 m from the pivot point, causing a clockwise torque. What is the net torque about the pivot? A: -.60 Nm

13. A disk has a moment of inertia of 3.0 x 10^-4 kgm^2, and it rotates with an angular speed of 3.5 rad/sec. What is the magnitude of the net torque must be applied to bring it to rest in 3.0 s? A: 3.5 x 10^-4 Nm

15. A solid sphereof mass 4.0 kg and a radius of 0.12 m is at rest at the top of a ramp inclined 15 degrees. It rolls to the bottom without slipping. The upper end of the ramp is 1.2 m higher than the lower end. What is the linear speed of the sphere when it reaches the bottom of the ramp? A: 4.1 m/s

THANK YOU!!!!