You are designing a new roller-coaster. The main feature of this particular design is a vertical circular loop. At the top of the loop, riders will feel like they are weightless when they are completely upside-down. Explain why such an effect is independent of the mass of the rider. Compute the radius of the loop required for this effect to occur if the coaster start at rest a height of 80m above the ground, speeds up as it descends to ground level, and then enters the loop.(You can assume that the coaster rolls on the track without friction).

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?

What’s #16 asking and how do i solve it?