Gravity: forces at a distance
Answers are for parents and teachers.
1
List three contact forces and three field forces from daily life.
Answers differ. Contact: friction, a push, elasticity. Field: gravity, magnetic force, electric force.
2
A school bag has a mass of 6 kg. What is its weight on Earth (g = 10 N/kg)?
6 × 10 = 60 N.
3
A friend says: “There is no gravity in space, so astronauts float.” Correct this.
Gravity still acts: at the space station it is about nine tenths as strong as on the ground. Astronauts float because they fall around the Earth with the station.
4
Build a small bridge from straws or card between two piles of books and find how many coins it can hold. Make it stronger and test again. Tidy up carefully.
Answers differ. Folding or adding supports usually helps. The coins add weight pulling the bridge down.
5
A person has a mass of 30 kg. Give the mass and the weight on the Moon, using g = 10 ÷ 6 N/kg.
Mass 30 kg; weight about 50 N.