Why would an orange roll off your cafeteria tray if you stopped suddenly? the net force on the orange is zero. the orange’s inertia keeps it in motion. rolling friction puts the orange in motion. gravity acts on the orange.

The orange roll off the tray due to inertia of motion.

Explanation:

As we move carrying the tray and orange placed on it at rest, the orange and the tray moves together with our body. As we suddenly stop, the tray and our body comes to rest instantly since they are in contact. The orange placed on tray keeps moving due to inertia of motion and hence rolls of your tray.

b. lifting dumbbell weight at 20-degree angle from the body after a 45-degree angle