How do i explain to kids how much water on earth is drinkable?

The thinnest layer of the earth is the:

A 0.4 kg object that stretches a spring 8.8 cm from its natural length when hanging at rest oscillates with an amplitude of 4.1 cm. Find the total energy of the system. The acceleration due to gravity is 9.81 m/s2. Answer in units of J.

A disk with a hole has inner radius rin and outer radius rout. the disk is uniformly charged with total charge q. find an expression for the on-axis electric potential at distance z from the center of the disk

In the forest (phrase-noun, but no subject and no verb) Smashing against the bat (phrase-verb but no subject) Before our first class (phrase) After the snowstorm (phrase) I am aware of the error (clause-subject and verb) When the saints go marching

Can someone explain the normal force? where does it come from? ... ?

The wavelength of sound wave is 30 m. Frequency is 7 Hz. What is the wave speed

The blood vessels that carry blood away from the heart to the rest of the body are

Mary has been playing an extreme form of dodge ball, where she has to stand on a board and try not to fall off as objects are thrown at her. Which of the following skills should she improve to do well at this game?

Examine the reactants of the incomplete double-displacement reaction. 2NaCl + H2SO4 → _[blank]_. What is the product of the double-displacement reaction?

A radio wave has a wavelength of 300 m. The wave moves with a speed of 3.0 * 108 m/s. What is the frequency of the radio wave? A. 1.0 * 106 Hz B. 1.0 * 10-5 Hz C. 1.0 * 10-6 Hz D. 1.0 * 105 Hz