Answer the following physics questions:

1. Calculate the value of the gravitational field strength g, 250 km above the surface of Earth. (rE = 6.38 x 10^6 m, ME = 5.98 x 10^24 kg) 2. The International Space Station is in orbit about 420 km above the surface of Earth. Calculate how many minutes it would take for the ISS to complete one orbit. (rE = 6.38 x 10^6 m, ME = 5.98 x 10^24 kg) 3. How much work is done against gravity to move a 720 kg weather monitor 120 km into the air? (rE = 6.38 x 10^6 m, ME = 5.98 x 10^24 kg) 4. List TWO differences between charging an object by contact and charging an object by friction 5. Two equal charges of magnitude 1.1 x 10^-7C experience an electrostatic force of 4.2 x 10^-4N. How far apart are the centres of the two charges? 6. Calculate the electric field 1.0 m from a small sphere with a positive charge of 3.2 x 10^-3C. Describe the direction as outwards or inwards. 7. A uniform electric field has a strength of 120 N/C. An alpha particle with a charge +2e is pushed against the field direction by an external force for a distance of 25 cm. How much electric potential energy does the alpha particle gain? 8. In a Millikan-type experiment, two horizontal parallel plates are 1.0 cm apart. A sphere of mass 2.2x10^-13 kg remains stationary when the potential difference between the plates is 350 V with the upper plate negative. a) Is the sphere positively or negatively charged