A "screen" or even just a set of parallel bars are highly reflective to electromagnetic waves as long as the open spaces are small compared to the wavelengths.
"Grid" dishes work fine ... with less weight and less wind resistance ... for frequencies below about 3 GHz. (Wavelengths of at least 10 cm.)
(I even worked on a microwave system in South America where huge grid dishes were used on a 90-mile link.)
The amount of work the two tugboats completed on the supertanker W = 3.12 × 10^9 joules .
Work is a physics term used to describe the energy transfer that takes place when an object is moved over a distance by an external force, at least some . The component of the force acting along the path multiplied by the length of the path can be used to calculate work if the force is constant. Mathematically, this idea is expressed as W = fd, where W is the work and f is the force multiplied by d, the distance. Work is completed when the force is applied at an angle of with respect to the displacement. Performing work on a body involves moving it in its entirety from one location to another as well as other methods. However, the work is thought to be negative if the applied force is in opposition to the item's motion, indicating that energy is being pulled away from the object
Learn more about work here:
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Answer:
k = 138440 N/m
Explanation:
given,
Mass of the car = 1200 Kg
speed of the car = 85 km/h
= 85 x 0.278 = 23.63 m/s
KE of the car
Using Spring Energy Formula
Using conservation of energy
k = 138440 N/m
Spring stiffness constant of the spring is equal to k = 138440 N/m