Idea 4of 7Builds onThe squeeze sets the priceChange needs a net force
The leftover force
Push 30 N, drag 15 N, 5 kg. Acceleration?
Today you'll discover
- the three lines every drag problem runs
- why the push alone gives the wrong answer
- the pull that makes the crate hold a steady speed
Think first30 N push, 15 N drag, a 5 kg crate
30 N push, 15 N drag, 5 kg. The crate's acceleration?
Decide first, then press Next. Follow the three lines in order.
A box on a floor with its push to the right and drag to the left labelled. After a prediction, the upward normal arrow is labelled, then the drag with its price, then the net arrow beside the box. The last step shortens the push to match the drag and asks what pull keeps the speed steady.
See the whole ideathe big idea and the key word, in one place
The big idea
Squeeze, drag, then give the leftover to Newton.
Easy to get wrongThe push alone is not the force in the second law. Subtract the drag first. On a level floor the up and down forces cancel and never enter the sideways story.
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?
- Run the three lines on a described crate and give its acceleration with a direction.