Pairs, diagrams, and the pull of Earth

Before this sitting

Can you already do this?

Two quick checks on “you will be able to…”. Right on both and this sitting becomes mixed practice, not a lecture. Wrong is useful — we keep the full sitting.

1. A bat hits a ball. During contact the force of bat on ball is 80 N east. The force of ball on bat is…

   ALess than 80 N, because the ball is lighterB80 N west, on the bat, so it does not cancel the 80 N on the ballC80 N east, so they addDZero once the ball leaves

2. A 3 kg box sits. g = 10 N/kg. Which sentence is true?

   AIts mass is 30 kg and its weight is 3 NBIts mass is 3 kg and its weight is 30 N downCMass and weight are both 3 kgDWeight is 3 kg, mass is 30 N