If a radioactive material has a half-life of 15 y what fraction of the material will remain after 30 y

Distinguish between theoretical mechanical advantage. How would these compare if a machine were 100percent efficient?

Why are buffers important in living organisms? Buffers prevent pH changes in body systems Buffers cause acids to break down food Buffers make bases work more effectively Buffers kill bacteria and viruses

A man drops a rock into a well. (a) the man hears the sound of the splash 2.90 s after he releases the rock from rest. the speed of sound in air (at the ambient temperature) is 336 m/s. how far below the top of the well is the surface of the water

If an electric circuit was analogous to a water park, then the electric current would be analogous to the a. pipes which carry the water through the circuit b. the people which flow from the top of the water ride to the bottom of the water ride c.

Will every solid with the same dimensions have the same density? Explain your answer.

Which factor will affect the light-gathering power of a telescope? A. change in the focal length B. change in the diameter of the objective C. change in the angle of the objective D. change in the elevation of the telescope E.

What is the acceleration of a 30.0-kg go kart if the thrust of its engine is 300.0 N?

Which of the following correctly compares a scientific investigation to a demonstration

You push a 45 kg wooden box across a wooden floor at a constant speed of 1.0 m/s. The coefficient of kinetic friction is 0.25. Now you double the force on the box. How long would it take for the velocity of the crate to double to 2.0 m/s

What is the middle layer of earth called