A proton with mass 1.67 x 10−27 kg and charge +1.6. x 10−19 C, is sent with velocity 2.3 x 104 m/s in the +x direction into a region where there is a uniform electric field of magnitude 780 V/m in the +y direction. What must be the magnitude and direction of the uniform magnetic field in the region if the proton is to pass through undeflected?
Assume that the magnetic field has no x-component and neglect gravitational effects.

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?