Charging by Contact examples​

James is trying to prove newton's 2nd law of motion. he tries to move four different objects with different masses, shapes, and sizes from point a to point b. the objects are a toy car, a car, a refrigerator, and a kitchen table. after some experimentation, he finds that force is dependent on the mass of the object, rather than it's size or shape. the object that takes the most force to move is the

Give one example to show that when substances are mixed,it may result in a chemical or a physical change depending on the conditions.

What kind of simple machine is a catapult?