Why is it more difficult to do a sit up with your hands behind your head than when your arms are stretched out in front of you?

When happens when an object becomes positively charged?

Hot coffee in a mug cools over time and the mug warms up. Which describes the energy in this system?

A catapult used by medieval armies hurls a stone of mass 32.0 kg with a velocity of 50.0 m/s at a 30.0 degree angle above the horizontal. What is the horizontal distance traveled when the stone returns to its original height? Ignore air resistance.

Consider a solid cylinder disk rotating on an through its center. if the angular momentum of the disk increases, what can you conclude

When a high-mass star explodes, which of the following is left over in the center? A. Black hole B. Neutron star C. White Dwarf D. either a or b

Which of the following is the most accurate statement concerning the properties of matter? a. they can be written as symbols b. they can be observed and measured c. they cannot be tested or verified d. they change with the amount of matter present

Danilo is sliding down a slide. What forces are acting on him as he slides

If you want your investment or savings account to be easily turned into cash without losing its value, you should consider the?

What is the definition of "gravitational potential energy"?

A number of food chains linked together