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Considering that the pulley is fixed, the force applied should be equal to the weight of the object - of 400N.

Pulleys or pulleys are mechanical tools used to assist in the movement of objects and bodies. There are two types of pulleys: fixed and movable. While the fixed pulley changes the direction of force, the moving pulley helps to decrease the force needed to move the object or body in question.
As the statement only tells us a pulley, we must consider that it is fixed, <u>because generally when it is mobile, this information is highlighted in the question</u>.
In this way, a fixed pulley only changes the direction of the applied force. Thus, the force must have the same magnitude as the weight of the object to be moved. If the bucket weighs 400N, the force applied to the pulley must be 400N.
<u>Therefore, having a fixed pulley, the force applied must be equal to the weight of the object, and will be 400N.</u>
Answer:
Magnetic force is equal to 
Explanation:
We have given electron is accelerated with a potential difference of 81700 volt.
Magnetic field B = 0.508 T
Angle between magnetic field and velocity 
Mass of electron 
Charge on electron 
By energy conservation.



Magnetic force on electron



In emission nebulae, there are interstellar clouds of hydrogen, which glow red because of the intense radiation of hot stars inside the nebula
So, the average speed of the Cheetah is 17.6 m/s.
<h3>Introduction</h3>
Hello ! I'm Deva from Brainly Indonesia. This time, I will help regarding the average speed. The average speed is obtained from finding the average of the speeds that occur or can be detected from the division between distance and travel time. The average speed can be formulated by :

With the following condition :
= average speed (m/s)- s = shift or distance objects from initial movement (m)
- t = interval of the time (s)
<h3>Problem Solving</h3>
We know that :
- s = shift = 88 m
- t = interval of the time = 5 seconds
What was asked :
= average speed = ... m/s
Step by step :



So, the average speed of the Cheetah is 17.6 m/s.
The ancient astronomers think areas of the moon called mares might be Seas.
Option D
<u>Explanation</u>:
The surface area of Earth's moon is dark, large, and is basaltic plains which are formed by ancient volcanic eruptions. They were dubbed as Maria, "ancient astronomers" who misunderstood them as actual seas. They are less reflective than highlands. Due to their iron-rich composition, they tend to appear dark from the naked eye. The Maria cover approximately about 16% of surface mostly on side that is visible from Earth. The few Maria on side that is too far are much smaller and residing mostly in very large craters. The ancient astronomers mistook the surface area as look like actual seas.