The angle of inclination is calculated using sin
function,
sin θ = 5 m / 20 m = 0.25
θ = 14.4775°
<span>The net force exerted is then calculated:
F net = m g sin θ = 20 * 9.8 * 0.25 </span>
F net = 49N
<span>Work is product of net force and distance:
W = F net * d = 49 * 20 </span>
<span>Work = 980 J </span>
Lower resistivity means higher conductivity: among these materials, the best conductor is silver, therefore it must be the material with lowest resistivity among those. We can also have a look at the value of resistivity of the different materials listed in the problem, to check our answer. The resistivities of the materials are the following:
Wood:

Salt water:

Silver:

Lead:

<span>We see that the material with lowest resistivity among those is silver, therefore the correct answer is silver.</span>
Answer:
the angle of reflection equals the angle of incidence—θr = θi. The angles are measured relative to the perpendicular to the surface at the point where the ray strikes the surface.
Explanation:
A microscope uses a mirror to reflect light to the specimen under the microscope. ... An astronomical reflecting telescope uses a large parabolic mirror to gather dim light from distant stars. A plane mirror is used to reflect the image to the eyepiece.
The needle on a compass always points in the direction of magnetic north because of the magnetic poles of earth. the compass is essentially a magnet itself, so the southern pole of the compass is attracted to the northern pole of earth.