See coulomb's law. Force is inversely proportional to the distance squared. So if you multiply r by 2, the force is multiplied by (½)² = ¼.
a. F/4
Explanation:
First, we need to determine the distance traveled by the car in the first 30 minutes,
.
Notice that the unit measurement for speed, in this case, is km/hr. Thus, a unit conversion of from minutes into hours is required before proceeding with the calculation, as shown below

Now, it is known that the car traveled 40 km for the first 30 minutes. Hence, the remaining distance,
, in which the driver reduces the speed to 40km/hr is
.
Subsequently, we would also like to know the time taken for the car to reach its destination, denoted by
.
.
Finally, with all the required values at hand, the average speed of the car for the entire trip is calculated as the ratio of the change in distance over the change in time.

Therefore, the average speed of the car is 50 km/hr.
Answer:
Best explains Jamming
Explanation:
<em>The deliberate radiation of electromagnetic (EM) energy to degrade or neutralize the radio frequency long-haul supervisory control and data acquisition (SCADA) communications links, best explains what?</em>
Jamming is defined as the blocking or interference with authorized wireless communications. it's a problem in personal area network wireless technologies. Jamming can occur inadvertently due to high levels of noise .
Jammers can send radio signals to interfere or disrupt communication flows by by decreasing the signal-to-noise ratio.They use radio frequency to interfere with communications by keeping it busy.
Answer:
Explanation:
A
Those devices the hold up while the pitcher is pitching measures speed. It has nothing to do with weather and temperature.