In a solar water heater, energy from the sun is gathered by water that circulates through tubes in a rooftop collector. the solar radiation enters the collector through a transparent cover and warms the water in the tubes; this water is pumped into a holding tank. assume that the efficiency of the overall system is 15.0% (that is, 85% of the incident solar energy is lost from the system). what collector area is necessary to raise the temperature of 210 l of water in the tank from 16°c to 41°c in 2.1 h when the intensity of incident sunlight is 790 w/m2? the specific heat of water is 4186 j/kg·k. the density of water is 1.00 g/cm3.

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

the aurora is formed when charged particles emitted from the sun during a solar flare penetrate the earth's magnetic shield and collide with atoms and molecules in our atmosphere. these collisions result in countless little bursts of light, called photons, which make up the aurora.

auroras are generated by charged solar particles hitting molecules in earth's atmosphere. this usually happens in high latitudes, because our planet’s magnetic field tends to funnel these particles toward the poles. that’s why it can be experienced in northern ohio.

490 n

f=125n a=2.5m/s2

365.25 earth days are in the year of a light year