An old door is very hard to open until oil is sprayed on its hinges. What does the oils do?

A) It increases the force of friction

B) It increases the force of gravity

C) It reduces the force of gravity

D) It reduces the force of friction

Question: Why is DNA useful in tracing evolutionary changes? A) DNA contains only elements, so it does not react easily. B) Many organisms do not contain DNA. C) Certain mutations in DNA happen at a constant rate.

100 meters toward the shore in 25 seconds

What is the sequence of energy transformations associated with a hydroelectric dam?

A block of mass 10 kg slides down an inclined plane that has an angle of 30. If the inclined plane has no friction and the block starts at a height of 2 m, how much kinetic energy does the block have when it reaches the bottom?

In this experiment you will use the Hall Effect to measure the strength of magnetic fields. Which of the following are true statements about the Hall Effect? (Select all that apply.) a.

An object has an acceleration of 24 m/s/s. How long would it take the stationary object to reach a velocity of 6.8 m/s?

What is normal distribution in statistics?

Which of the following water samples would be considered acidic

A linearly-polarized electromagnetic (EM) wave has an electric field with amplitude 1000 V/m. You hold a a linear polarizer in front of it and rotate the polarizer so that all of the EM wave is blocked. You then rotate the polarizer 30 degree.

Let y'=4 x. find all values of r such that y = rx^{2} satisfies the differential equation. if there is more than one correct answer, enter your answers as a comma separated list.