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MrRa [10]
3 years ago
6

As a runner crosses the finish line of a race, she starts decelerating from a velocity of 9 m/s at a rate of 2 m/s^2. Take the r

unner's velocity as she crosses the finish line to be in the positive direction. What is the runner’s displacement, in meters, during the first 5 seconds after crossing the finish line?
What is her velocity, in meters per second, 5 seconds after crossing the finish line?
Physics
1 answer:
Ksivusya [100]3 years ago
4 0

Answer:

- 1 m/s, 20 m

Explanation:

u = 9 m/s, a = - 2 m/s^2, t = 5 sec

Let s be the displacement and v be the velocity after 5 seconds

Use first equation of motion.

v = u + a t

v = 9 - 2 x 5 = 9 - 10 = - 1 m/s

Use second equation of motion

s = u t + 1/2 a t^2

s = 9 x 5 - 1/2 x 2 x 5 x 5

s = 45 - 25 = 20 m

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A force of gravity pulls downward on a book on a table. What force prevents the book from accelerating downward?
Nadusha1986 [10]

Answer: The Normal Force

Explanation:

According to Third Newton's Law,  also konwn as The principle of action and reaction :

<em>"If a body A exerts an action on another body B, it performs on A another action that is the same and in the opposite direction."</em>

In this case this is what happens with the book on a table,  gravity force pulls it downward, but the Normal Force (perpendicular to the surface of the table) acts in the opposite direction with the same magnitude, preventing the book from accelerating downward.

3 0
3 years ago
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An elevator of massmis initially at rest onthe first floor of a building. It moves upward,and passes the second and third floors
Varvara68 [4.7K]

To solve this problem it is necessary to apply the concepts of Work. Work is understood as the force applied to travel a determined distance, in this case the height. The force in turn can be expressed by Newton's second law as the ratio between mass and gravity, as well

W = mgh

Where,

m = mass

h = height

g = Gravitational constant

When it ascends to the second floor it has traveled the energy necessary to climb a height, under this logic, until the 4 floor has traveled 3 times the height h of each of the floors therefore

h = 3h

Replacing in our equation we have to

W = mgh\\W = mg(3h)\\W = 3mgh

The correct answer is 4.

7 0
3 years ago
An atom has an atomic number 17 and atomic mass number 35. How many neutrons are present in its nucleus?
Anna [14]
The number of <span>neutrons that are present in its nucleus is 18. The correct option among all the options that are given in the question is the second option or option "B". Mass number minus the atomic number gives the number of neutrons. I hope that this is the answer that has come to your help.</span>
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3 years ago
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A car, traveling at , encounters a dip in the road. The radius of curvature at the bottom of the dip is . Each of the car’s four
labwork [276]

Answer:

spring deflection is  x = (v2 / R + g) m / 4

Explanation:

We will solve this problem with Newton's second law. Let's analyze the situation the car goes down a road and finds a dip (hollow) that we will assume that it has a circular shape in the lower part has the car weight, elastic force and a centripetal acceleration

 

Let's write the equations on the Y axis of this description

       Fe - W = m a_{c}

Where Fe is elastic force, W the weight and a_{c}  the centripetal acceleration. The elastic force equation is

       Fe = - k x

     

       4 (k x) - mg = m v² / R

The four is because there are four springs, R is theradio of dip

We can calculate the deflection (x) of the springs

       x = (m v2 / R + mg) / 4

       

       x = (v2 / R + g) m / 4

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A Newton is a unit of...
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Answer:

A newton is a unit of measurement. Please mark me brainliest:)

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