The mechanical force of contraction is generated by

What is the approximate percentage of geologic time that humans have existed on earth since its origin?

Why is the amount of mechanical energy produced less than the amount of electrical energy used?

An element is a substance composed of atoms that all have the same number of protons. A. True B. False

2. The nucleus holds two particles: a. proton and electron b. proton and neutron c. neutron and electron

17. A distance-time graph indicates that an object moves 120 meters in 5 seconds and then remains at rest for 5 seconds. What is the average speed of the object?

As an astronaut travels towards Earth, her weight A. decreases because gravity decreases. B. decreases because her mass decreases. C. increases because gravity increases. D. remains the same because her mass remains the same.

Lightning often strikes water. a. True b. False

How much work must be done on a 10 kg snowboard to increase its speed from 4 m/s to 6 m/s?

If a spacecraft that seems to be motionless in deep space is given some type of quick push, what will happen? A. The spacecraft will not move because it only works on earth. B.

A fast, white water cascade is also known as what?