1. Gravitational Field Strength & Satellites

2. Gravitational Field Strength Gravitational force per unit mass on an object g = F g / m (units = N/Kg) g = gravitational field strength F g = Force of gravity (also weight) m = mass

3. Gravitational Field Strength Example Problem: While in orbit in the space shuttle, the gravitational field strength on an astronaut is 7.83 N/Kg. 1. How much does an 80 kg astronaut weigh on the shuttle? 2. How much does the astronaut weigh on Earth?

4. Gravitational Field Strength Problem How much does an 80 kg astronaut weigh on the shuttle? g = F g / m (solve for F g ) F g = (7.83 N/Kg) x (80 Kg) = 626.4 N (we don’t express in N) = 626.4 N x.22 lbs/N = 137.8 lbs

5. Gravitational Field Strength Problem How much does the astronaut weigh on Earth? F g = (9.8 N/Kg) x (80 Kg) = 784 N = (784 N) x (.22 lbs/N) = 172.5 lbs

6. Satellite Speed & Period Remember, to solve for altitude you must include the radius of the Earth To solve for altitude, use the equation a = v 2 (solve for “r”) r speed / velocity: v = sqrt Gxm / r period: T = 2π x sqrt R 3 GM

7. Satellite Speed & Period When solving these problems, you use the “M” – the large mass that the satellite is revolving around “R” – the radius / altitude of the satellite above the object it is orbiting