Why are some rocks smooth and others rough?

1400 kg car has a speed of 27 m/s. if it takes 7 s to stop the car, what is the impulse and the average force acting on the car?

Imagine you work as a consultant, and your daily job involves listening to the constructive criticism of others. as part of your job, you must listen to opposing viewpoints to make important decisions. in this activity, you are a consulting dam engineer. you must make a decision about four different dams; should they be repaired, taken down, or left alone? you will listen to contrasting opinions about what should be done with the dams before you make the final decision. as the consulting dam engineer, what do you decide to do with this dam? explain your reasoning. by making your decision, did you support the opinions of the mayor and/or the dam safety official? why or why not? (site 1)

Which types of electromagnetic waves have higher frequencies than the waves that make up ultraviolet light? check all that apply. radio waves infrared light microwaves gamma rays visible light x-rays