Idea 4of 6Builds onChange needs a net forceEarth pulls everything
Mass fights back
Why is a loaded cart harder to get moving?
Today you'll discover
- what the same push does to a heavier cart
- the difference between hard to lift and hard to start
- why mass is the measure of reluctance
Think firstThe same push, on a loaded crate
Load the crate with more mass and push just as hard. What changes?
Decide first, then press Next. Watch which arrows change and which do not.
A box on a floor with a hand's push drawn as an arrow to the right. After a prediction, Earth's pull is highlighted as the lifting cost, then the push alone as the starting cost. The net arrow and the box's mass are shown together. The last step asks which of two carts changes velocity more for the same shove.
See the whole ideathe big idea and the key word, in one place
The big idea
Inertia is how much an object resists change; mass measures it.
Compare themA weightless crate in orbit is still hard to shove. Weight needs a planet; mass does not.
Key word
- inertia
- an object's tendency to keep its velocity, rest included, unless a net force acts; mass is its measure
About this modelArrows are forces, not motion: a box can move with no arrow pointing its way.
Arrows are forces, not motion: a box can move with no arrow pointing its way.
Ready to use it?
- Say which of two objects changes velocity more for the same net force, and why.