Galileo’s principle and motion in a gravitational field
Answers are for parents and teachers.
1
A train moves at 18 m/s. A person walks forward in the carriage at 3 m/s relative to it. What is the speed relative to the ground (m/s)?
21
2
A river flows at 2 m/s and a boat moves against the current at 5 m/s relative to the water. What is its speed relative to the bank (m/s)?
3
3
A 0.5 kg ball hangs on a string in a cart accelerating at 5 m/s². What is the magnitude of the inertial force (N)?
2.5
4
Near the Earth’s surface g = 10 m/s² and R = 6400 km. What is the first cosmic velocity (m/s)? (υ = √(gR))
8000
5
Why are artificial satellites usually put into orbits at least 300 km above the Earth’s surface?
At that height the air is very thin and there is almost no air resistance; lower down the air would slow the satellite and bring it down.