Find Net Force From a Speed Time Graph

Use the elevator sheet first to set up balanced and unbalanced forces. Then use the graph and ski slope sheets for F = m × a, and finish with the two force pair sheets.

Graph a 90 kg scooter and rider speeding up, cruising and braking, then find net force with F = m × a. The directions on the page read: Plot and connect the data. Use slopes and F = m × a to fill in the table. Then answer. An answer key is included.

Yes, both. We made it for 8th grade forces and motion, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

Net force is the sum of all the forces on an object, with direction. When it is zero, the object keeps the same speed and direction. When it is not zero, the object speeds up, slows down or turns, with a = F / m.

The two forces in a pair are equal and opposite, but they act on different objects. On a water rocket, Earth pulls the rocket and the rocket pulls Earth, so the forces never cancel on either one. Force Pairs in a Water Rocket Launch makes this point.

While it speeds up, the floor must push harder than gravity pulls, so the scale reading rises. On the elevator sheet, Lena's 490 N weight reads 550 N while the elevator speeds up. At a steady speed it reads 490 N again.