Which will produce a magnetic field?

How many seconds does it take a pebble released from rest off a bridge to fall 29.4 m ? what is the pebble's speed when it has fallen 29.4 m ?

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

Carmen is load furniture and boxes onto a moving truck. she picks up boxes of her things, places them on a cart, and pushes the cart to the moving van. which term best describes the type of force carmen uses? a. contact b. friction c. gravity d. noncontact