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Dmitrij [34]
3 years ago
14

A car is traveling at 120 km/h (75 mph). When applied the braking system can stop the car with a deceleration rate of 9.0 m/s2.

The typical reaction time for an alert driver is 0.8 s versus 3 s for a sleepy driver. Assuming a typical car length of 5 m, calculate the number of additional car lengths approximately it takes the sleepy driver to stop compared to the alert driver. Group of answer choices
Physics
1 answer:
Bumek [7]3 years ago
8 0

Answer:

the number of additional car lengths approximately it takes the sleepy driver to stop compared to the alert driver is 15

Explanation:

Given that;

speed of car V  = 120 km/h = 33.3333 m/s

Reaction time of an alert driver = 0.8 sec

Reaction time of an alert driver = 3 sec

extra time taken by sleepy driver over an alert driver = 3 - 0.8 = 2.2 sec

now, extra distance that car will travel in case of sleepy driver  will be'

S_d = V × 2.2 sec

S_d = 33.3333 m/s × 2.2 sec

S_d = 73.3333 m

hence, number of car of additional car length  n will be;

n = S_n / car length

n = 73.3333 m / 5m

n = 14.666 ≈ 15

Therefore, the number of additional car lengths approximately it takes the sleepy driver to stop compared to the alert driver is 15

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A tank is full of water. Find the work W required to pump the water out of the spout. (Use 9.8 m/s2 for g. Use 1000 kg/m3 as the
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Answer:

W = 1.06 MJ

Explanation:

- We will use differential calculus to solve this problem.

- Make a differential volume of water in the tank with thickness dx. We see as we traverse up or down the differential volume of water the side length is always constant, hence, its always 8.

- As for the width of the part w we see that it varies as we move up and down the differential element. We will draw a rectangle whose base axis is x and vertical axis is y. we will find the equation of the slant line that comes out to be y = 0.5*x. And the width spans towards both of the sides its going to be 2*y = x.

- Now develop and expression of Force required:

                                             F = p*V*g

                                             F = 1000*(2*0.5*x*8*dx)*g

                                             F = 78480*x*dx

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                                             W = F.s

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                                             s = (5 - x)

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                                            dW = 78400*x*(5-x)dx

- Now integrate the following express from 0 to 3 till the tank is empty:

                                           W = 78400*(2.5*x^2 - (1/3)*x^3)

                                           W = 78400*(2.5*3^2 - (1/3)*3^3)

                                           W = 78400*13.5 = 1058400 J

 

5 0
3 years ago
Natasha weighs 530N. what is her kinetic energy as she swimsat
WITCHER [35]

<u>Answer:</u> The kinetic energy of Natasha as she swim is 38.88 J

<u>Explanation:</u>

Force is defined as the mass multiplied by the acceleration of the object.

Mathematically,

F=m\times a

where,

F = weight of Natasha = 530 N

m = mass of Natasha = ?

a = acceleration due to gravity = 9.8m/s^2

Putting values in above equation, we get:

530kg.m/s^2=m\times 9.8m/s^2\\\\m=\frac{530}{9.8}=54kg

Speed is defined as the rate at which an object moves with respect to time.  To calculate the speed, we use the equation:

s=\frac{d}{t}

where,

d = distance traveled = 72 m

t = time taken by Natasha = 1.0 min = 60 sec   (Conversion factor:  1 min = 60 s)

Putting values in above equation, we get:

s=\frac{72}{60}=1.2m/s

Kinetic energy is defined as the energy which is possessed due to its motion.  It is also defined as the half of the product of mass of the object and square of the velocity of the object.

Mathematically,

E_K=\frac{1}{2}mv^2

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v = velocity of Natasha = 1.2 m/s

Putting values in above equation, we get:

E_K=\frac{1}{2}\times 54\times (1.2)^2\\\\E_K=38.88J

Hence, the kinetic energy of Natasha as she swim is 38.88 J

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