1. Calculate the force of gravity on a spacecraft 12,800km above the earth's surface if it has a mass of 700kg.
2. Each of two spheres 6.0e-2m apart carries a charge of 2.0e-6C.
a. Calculate the force between them.
b. Is the force attractive or repulsive?
3. What is the magnitude and direction of the force on an electron travelling at 100,000m/s east in a 1.5T magnetic field directed vertically upward?
