Physics Starter Trail | Knowledge Mountain

FIRST, A FEW USEFUL IDEAS

Three notes for the trail.

FIELD NOTE / Physics

Position, velocity, acceleration: three different questions

Position tells you where an object is. Velocity tells you how its position changes with time and includes direction. Acceleration tells you how velocity changes with time. An object can have zero velocity at an instant and still have nonzero acceleration.

A way to rememberWhere? How fast and which way? How is that changing?

At the top of a ball’s vertical flight, is gravity’s acceleration zero?

No. Its vertical velocity is momentarily zero, but acceleration due to gravity still points downward.

FIELD NOTE / Physics

Falling starts slowly, then speeds up

For an object released from rest near Earth with no air resistance, downward displacement is h = ½gt² and speed is v = gt. Doubling the fall time makes the distance four times as large, while the speed doubles. Here we take downward as positive.

A way to rememberTime squared stretches the fall.

After 2 seconds in this model, how far has an object fallen?

h = ½ × 9.8 × 2² = 19.6 metres. This requires enough height to keep falling for 2 seconds.

FIELD NOTE / Physics

Every model has a boundary

The simple fall model ignores air resistance and treats gravity as constant. It can describe a compact object over a short drop reasonably well. A feather, parachute, or very long fall needs more information. Changing mass does not change ideal free-fall acceleration, but real drag depends on factors such as shape and speed.

A way to rememberA model is useful because you know what it leaves out.

Would a feather and a metal ball fall together in a vacuum?

In the same gravitational field, yes: with no air drag they have the same acceleration regardless of mass.

The Motion Studio

Three notes for the trail.

Position, velocity, acceleration: three different questions

Falling starts slowly, then speeds up

Every model has a boundary

Predict. Release. Explain.

What stayed with you?