When did the last mass extinction occur?

What equals the number of protons in an atom

Interference is evidence of the particle nature of light. true or false

The emission spectrum of an atom provides information primarily regarding?

a car moves from a to b at a speed of 50km per hr and comes back from b to a at a speed of 30km per hour. find its average speed during the journey

The volume of a gas increases from 18.7 m3 to 25.1 m3 while the pressure changes from 1.82 atm to 1.41 atm. If the initial temperature is 353 K, the final temperature of the gas is K.

Consider a helium balloon on a string tied to the seat of your stationary car. The windows are closed, so there is no air motion within the car. The car begins to accelerate forward. Which way will the balloon lean, forward or backward

The force of gravity acts upon meteors from the rocky asteroid belt between mars and Jupiter. Where is the force of gravity most likely to pull these meteors

Sally turns on her cellular telephone to speak to her friend who is located thousands of miles away. Which of the following best describes how such a telephone is able to transmit and receive information? A.

Calculate the gravitational potential energy relative to the ground when an 82 kg person climbs to the top of a 2.0 m stepladder.

A rock is thrown from a cliff and hits the ground five seconds later at a distance of 50 m from the cliff how high was a cliff