An unstrained horizontal spring has a length of 0.44 m and a spring constant of 238 N/m. Two small charged objects are attached to this spring, one at each end. The charges on the objects have equal magnitudes. Because of these charges, the spring stretches by 0.029 m relative to its unstrained length. Determine the possible algebraic signs and the magnitude of the charges.

Explanation:

Given that,

Length of the spring, l = 0.44 m

Spring constant of the spring, k = 238 N/m    

Two small charged objects are attached to this spring, one at each end. The charges on the objects have equal magnitudes.

Displacement in the spring, x = 0.029 m

The force acting on the spring is given by :

This force will act between charges as :

So, the magnitude of charge is and it has positive sign.

Geologists use seismic waves to locate the center of an earthquake.

Geologists use data from three or more data stations to determine the location of the epicenter.

A seismograph measures the difference between the arrivals of P waves and S waves.

Explanation:

Seismic waves refer to the energy within the Earth due to sudden movement and explosions. Basically, they are the energy traveling within the Earth, and this energy cause movement, an excess of it will cause major movements, causing damage in the surface.

So, the epicenter of a earthquake is tracked using seismic waves, but this process more complex that we thought, because geologists need to track the epicenter using other data stations which offer real time information about seismic waves. Using all this data, geologist can find the epicenter faster and accurately.

There are different types of seismic waves, there's the Primary Waves or P-Waves, they are called primary because they are the first to perceive by the seismic station, they push and pull constantly, like a spring. Another type of seismic waves is The Secondary Wave or S-Waves, this is slower than the first one, this type of waves can moves mass of rocks up and down, constantly perpendicular to its direction. These two types are called body waves, and they are used by geologist to locate an earthquake.

Lastly, we have the surface waves, which only travel through the crust. In this category we have Love Waves which are the fastest, moving side to side. Also, we have the Rayleigh Waves, which are waves that roll the ground like ocean waves roll the water.

Therefore, based on these definitions, there are three correct answers, first, third and last one.