At a distance of 0.75 meters from its center, a van der graff generator interacts as if it were a point charge, with that charge concentrated at its center. a test charge at that distance experiences an electric field of 4.5 × 10^5 newtons/coulomb. what is the magnitude of charge on this van der graff generator? a. 1.7 × 10^-7 coulombs b. 2.8 × 10^-7 coulombs c. 3.0 × 10^-7 coulombs d. 8.5 × 10^-7 coulombs

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?