Which statements about acceleration are true?

check all that apply.

a. the symbol for acceleration is .
b. for acceleration, you must have a number, a unit, and a direction.
c. to calculate acceleration, divide the change in velocity by the change in time.
d. the si units for acceleration are miles per hour per second.

How is coal extracted from mountaintop removal mines? a. dynamite is used to create underground tunnels where miners go to extract the coal. b. dynamite is used to break apart rocks and then draglines are used to remove the broken rock and reach the coal. c. coal in mountaintops is extracted by digging strips in the landscape to reach the coal. d. placer deposits in mountain river bottoms are removed by

Photons with the highest energy have the longest period

The first-order reaction a→2b+c has rate constant 0.538 s−1. if the initial concentration of a is 0.867 mol l−1, what is the half-life of the reaction in seconds? remember to use correct significant figures in your answer (round your answer to the nearest hundredth). do not include units in your response.