S4.8.5 For the adult
Weight and falling
A skydiver jumps from a plane. Why does she stop speeding up long before she lands?
What this chapter teaches
Weight is a force, W = m × g, with g = 9.8 N/kg on Earth. Mass does not change with place. A falling object speeds up until the drag equals the weight, and then its velocity is constant: the terminal velocity.
Three questions to ask
There is no one right wording. Listen for the idea.
- What is the weight of a 5 kg bag, and what would its mass be on the Moon?
- Why does a skydiver stop speeding up, and what has happened to the resultant force?
- Why does she slow down when the parachute opens, and why does she then settle at a lower speed?
After the chapter, the learner can
- Calculate weight from mass and gravitational field strength
- Explain terminal velocity using the forces on a falling object
- Time paper cones falling to show terminal velocity
What they copy into their notebook
Weight W = m × g, in newtons, with g = 9.8 N/kg on Earth. Mass does not change. A falling object has terminal velocity when drag = weight and the resultant is zero.