Does friction depends on the nature of two syrfaces which are in contact with each other

Problem 9) If you had light of wavelength 700nm when emitted, what would the wavelength be for an observer who is a red shift z = 0.05 from that source?

Atoms and elements are the basic back bone of the universe. Explain what this means and how the idea of the atom has changed over time.

An acorn falls from an oak tree. You note that it takes 2.5 seconds to hit the ground. How fast was it going when it hit the ground?

Sound waves travel at the rate of 343 m/s at 20°C. If a man standing 450 meters away from the wall of a canyon yells, "Hello," how long will it take for him to hear his own voice echo off of the wall?

Which examples of science than pseudoscience

Describe the factors that form deep currents

A comet is cruising through the solar system at a speed of 50000 kilometers per hour for 4 hours time. What is the total distance traveled by the comet during this time in kilometers, miles, and light years?

A gas in a closed container is heated with 12J of energy, causing the lid of the container to rise 3m with 5N of force. What is the total change in energy?

What are illuminated objects?

During one year a population of blue jays has zero population growth. which must be true about the blue jay population at the end of the year compared to the beginning of the year?