In April 1974, Steve Prefontaine completed a 10.0 km race in a time of 27 min , 43.6 s . Suppose "Pre" was at the 7.71 km mark at a time of 25.0 min . If he accelerated for 60 s and then maintained his increased speed for the remainder of the race, calculate his acceleration over the 60 s interval. Assume his instantaneous speed at the 7.71 km mark was the same as his overall average speed up to that time.

Answers

Answer 1

Answer:

0.18 m/s²

Explanation:

The total time taken to cover a 10 km race is 27 min, 43.6 seconds.

At 25 min, Pre was at 7.71 km mark. Therefore the average speed = 7.71 km / 25 min = 7710 m / (25 * 60) s = 5.14 m/s

The distance remaining = 10 km - 7.71 km = 2.29 km = 2290 m

The remaining time = 27 min, 43.6 seconds - 25 min = 2 min 43.6 second = 163.6 seconds

She accelerates for 60 seconds, therefore the distance covered (S) during the acceleration (a) is:

S₁ = 5.14(60) + 0.5a(60)² = 308.4 + 1800a

She maintains the speed for the remaining distance (S₂). The remaining time = 163.6 seconds - 60 seconds = 103.6 seconds. The final speed after the acceleration = (5.14 + 60a) m/s

S₂ = (5.14 + 60a)* 103.6 = 532.5 + 6216a

S₁ + S₂ = 2290 m

(308.4 + 1800a) + (532.5 + 6216a) = 2290

8016a + 840.9 = 2290

8016a = 1449.1

a = 0.18 m/s²


Related Questions

Which wave shows the loudest sound below?​

Answers

Answer:

I think C

Explanation:

If im right give brainliest :)

Answer: C the right answer

a man runs 1200m on a straight line in 4 min . find his velocity.

Answers

Answer:

5m/sec^2

Explanation:

Distance=1200m

Time=4 min

1=60sec

4=4 x 60

=240sec

Velocity=Distance/Time

Velocity=1200/240

Velocity=5m/sec^2

Mark me as brainliest

The motor of a battery-powered scooter can maintain a speed of 5.3 m/s by providing a force of 280 N. What is the power output of the motor? *

Answers

Answer:

the power output P = 1484 W

Explanation:

Power P  = Force× speed

Given that motor of a battery-powered scooter can maintain a speed of 5.3 m/s by providing a force of 280 N.

Therefore,the power output of the motor P = 280×5.3 = 1484 W

Hence, the power output P = 1484 W

How is an ammeter connected in a circuit to measure current flowing through it?

Answers

Answer:

It is connected in series with the circuit

Explanation:

This is because to measure the current in the circuit, the current in the circuit has to flow through the ammeter. As such, the ammeter must be connected in series with the circuit so as to measure the current flowing through the circuit.

So, to measure the current flowing through a circuit with an ammeter, the ammeter must be connected in series with the circuit.

As Courtney switches on the TV set to watch her favorite cartoon, the electron beam in the TV tube is steered across the screen by the field between two charged plates. If the electron experiences a force of 3.0 * 10^6 N, how large is the field between the deflection plates?

Answers

Answer:

Explanation:

Force= (q1q2)/(4/\Ęr2)

3×10^6= (1.602×10^-19)^2/(r^2)

r^2=(2.27×10^-33)/(3×10^6)

r^2=8.55×10^-45

r= 9.25×10^-23

a bell rings at a frequency of 75hz on a warm 25 degree evening. calculate the...
a. speed of the sound wave at this temperature.
b. wavelength of the sound wave

Answers

Answer:

Explanation:

We need 2 different equations for this problem: first the velocity of sound equation, then the frequency of the sound equation.

The velocity of sound is found in:

v = 331.5 + .606T

We need to find that first in order to fill it into the frequency equation which is

[tex]f=\frac{v}{\lambda}[/tex] where v is the velocity we will find the part a, f is frequency and lambda is the wavelength. Starting with the velocity of the sound:

v = 331.5 + .606(25) and

v = 331.5 + 15 and rounding correctly using the rules for sig fig when adding:

v = 347 m/s

Filling that into the frequency equation:

[tex]75=\frac{347}{\lambda}[/tex] and

[tex]\lambda=\frac{347}{75}[/tex] so

[tex]\lambda=4.6m[/tex]

goodie morning
—————————

what is nitric acid?​

Answers

Answer:

Nitric acid, also known as aqua fortis and spirit of niter, is a highly corrosive mineral acid. The pure compound is colorless, but older samples tend to acquire a yellow cast due to decomposition into oxides of nitrogen and water. Most commercially available nitric acid has a concentration of 68% in water.

Explanation:

Good morning...

Nitric acid production is mainly driven by fertilizer industry. Nitric acid is used in the production of ammonium nitrate and calcium ammonium nitrate which find applications as fertilizers.

(b) During one day, 250 kg of water is pumped through
the solar panel. The température of this
water rises from 16°C to 38°C.
The water absorbs 25% of the energy incident on the solar panel. The
specific heat capacity
of water is 4200J/(kg °C).
Calculate the energy incident on the solar panel during that day.
Please explain how to find the incident energy

Answers

Answer: The energy incident on the solar panel during that day is [tex]9.24 \times 10^{7} J[/tex].

Explanation:

Given: Mass = 250 kg

Initial temperature = [tex]16^{o}C[/tex]

Final temperature = [tex]38^{o}C[/tex]

Specific heat capacity = 4200 [tex]J/kg^{o}C[/tex]

Formula used to calculate the energy is as follows.

[tex]q = m \times C \times (T_{2} - T_{1})[/tex]

where,

q = heat energy

m = mass of substance

C = specific heat capacity

[tex]T_{1}[/tex] = initial temperature

[tex]T_{2}[/tex] = final temperature

Substitute the values into above formula as follows.

[tex]q = 250 kg \times 4200 J/kg^{o}C \times (38 - 16)^{o}C\\= 250 kg \times 4200 J/kg^{o}C \times 22^{o}C[/tex]

As it is given that water absorbs 25% of the energy incident on the solar panel. Hence, energy incident on the solar panel can be calculated as follows.

[tex]\frac{25}{100} \times q = 250 kg \times 4200 J/kg^{o}C \times 22^{o}C\\q = 9.24 \times 10^{7} J[/tex]

Thus, we can conclude that the energy incident on the solar panel during that day is [tex]9.24 \times 10^{7} J[/tex].

(b) How much energy must be supplied to boil 2kg of water? providing that the specific latent heat of vaporization of water is 330 kJ/kg.

Answers

Complete question:

(b) How much energy must be supplied to boil 2kg of water? providing that the specific latent heat of vaporization of water is 330 kJ/kg. The initial temperature of the water is 20 ⁰C

Answer:

The energy that must be supplied to boil the given mass of the water is 672,000 J

Explanation:

Given;

mass of water, m = 2 kg

heat of vaporization of water, L =  330 kJ/kg

initial temperature of water, t = 20 ⁰C

specific heat capacity of water, c = 4200 J/kg⁰C

Assuming no mass of the water is lost through vaporization, the energy needed to boil the given water is calculated as;

Q = mc(100 - 20)

Q = 2 x 4200 x (80)  

Q = 672,000 J

Q = 672,000 J

Q = 672,000 J

Therefore, the energy that must be supplied to boil the given mass of the water is 672,000 J

Multiplying a vector with another vector results in what type of answer.

A) a direction
B) a vector
C) either a vector or a scalar
D) a scalar

Answers

multiplication of two vectors yields a vector oroduy

the use of thermostat in a gas cooker is to ​

Answers

Explanation:

An oven thermostat regulates the temperature inside an oven. The thermostat's temperature-sensitive probe measures the oven's warmth, switching the heat on and off as necessary to maintain the correct temperature.

A rope horizontally pulls a massive object lying on a surface with friction with a constant
velocity. What describes the force on the rope?

Answers

Answer:

Equal to the frictional force

Explanation:

Question; The options given with regards to a similar question posted online are;

A. Equal (equivalent) to the frictional force

B. Larger than the frictional force

C. Equal to the object's weight

D. More than the object's weight

Explanation

According to Newton's first law of motion, every object shall remain at rest or continue moving with uniform (constant speed) motion unless there is a net force acting on the object

Given that the velocity of the massive block, lying on the surface that has friction, being pulled by the rope = Constant

Therefore;

The net force acting on the moving block while being pulled by the rope = 0

From which we have;

The pulling force = The resistive force

Where;

The pulling force = The (pulling) force (applied) on the rope

The resistive force = The frictional force of the surface which tends to prevent the motion of the block

Therefore, given that the net force acting on the block = 0

The force on the rope = The frictional force (of the surface)

The correct option is option A. Equal to the frictional force.

Vector B has components Bx = 6.18 and By = 4.43. Find the magnitude and direction counter clockwise from the positive x-axis.

Answers

Answer:

Explanation:

The formula for the magnitude of this resultant vector, which is in Q1, btw, is:

[tex]B_{mag}=\sqrt{6.18^2+4.43^2}[/tex] which gives us, to 3 sig fig's:

7.60 m. Since the resultant vector is in Q1, we don't need to add anything to the angle once we find it to 3 sig fig:

[tex]tan^{-1}(\frac{4.43}{6.18})[/tex] gives us an angle of 35.6 degrees

help please!!
From the following images shown, classify the interactions that occur and say between which bodies, according to the following criteria:
a) Contact forces
b) Non-contact forces

Answers

Answer:

B= 4 A=5

Explanation:

what are scalar quantities and list their examples​

Answers

Explanation:

these are quantities that have magnitude but no direction

Examples include : speed, mass, volume, density, everything, time

speed, mass, volume, density, time

Bones are composed of three main components, what are they? (Choose all that apply)

Answers

Answer:

funny bone and compact bone

Explanation:

your funny bone only reacts if you hit it against something the compact bone is the heaviest and strongest bone in your body and the bone marrow is soft sponge like tissue in the center if most bones that produces white and red blood cells

The velocity of sound in a medium increases with increasing

a. distance
b. amplitude
c. temperature
d. time​

Answers

c- temperature

The speed of sound increases with increasing temperature .

Which one of the following is an example of a solution?
a. Sand particles in water
b. Orange Squash
c. Vinegar
d. Paint

Answers

Answer:

it is maybe A but i'm not 100% sure

Explanation:

its the only one that is mixed

what is parking orbit?​

Answers

A parking orbit is a temporary orbit used during the launch of a spacecraft. A launch vehicle boosts into the parking orbit, then coasts for a while, then fires again to enter the final desired trajectory.

Hope this helps!

Have a great day :)

Answer:

A temporary orbit in which a spacecraft awaits the next phase of its mission .

(I have 2 questions which are very similar)
Which of the chemical reactions above stores energy?
A. Cellular respiration
B. Photosynthesis
C. Both cellular respiration and photosynthesis
D. Neither cellular respiration nor photosynthesis

15 Which of the chemical reactions above releases energy?
A. Cellular respiration
B. Photosynthesis
C. Both cellular respiration and photosynthesis
D. Neither cellular respiration nor photosynthesis
(help!!!) SCIENCE

Answers

Answer:

B

A

Explanation:

please mark as brainliest :)

10 points
Calculate the force of attraction between the moon and the earth, if their masses and distance apart are 10^22Kg, 10^24kg and 6.4x10^6m. Take g = 6.67x10^-11Nm^2Kg^-2
a) 0.63x10^24N
b) 1.63x10^22N
c) 2.63x10^20N
d) 3.63x10^18N​

Answers

Answer:

Explanation:

You didn't fill in the proper masses which is why you never got an answer to this. But that's ok...I got you. I happen to know what they are! We will use the universal law of gravitation and the gravitational constant to solve this.

[tex]F_g=\frac{Gm_1m_2}{r^2}[/tex] and filling in:

[tex]F_g=\frac{(6.67*10^{-11})(5.98*10^{24})(7.36*10^{22})}{(3.84*10^8)^2}[/tex] The denominator is the radius of the earth plus the radius of the moon plus the distance between their surfaces, just FYI.

That gives us that

[tex]F_g=1.99*10^{20}N[/tex] Not sure what your choices entail, but I'd have to say, taking into consideration that maybe your problem didn't figure in the distance between the surfaces, you'd be at choice B.

The energy of an electromagnetic wave changes proportionally to which

other property?

O A Speed

O B. Shift

O c. Wavelength

O D. Frequency

Answers

Answer:

D. Frequency

Explanation:

The energy of an  electromagnetic wave is proportional to frequency, mathematically it is expressed as;

E ∝ f

E = hf

where;

h is Planck's constant = 6.626 x 10⁻³⁴ Js

The equation above can also be expanded to;

[tex]E = hf = h \frac{c}{\lambda}[/tex]

where;

c is speed of light = 3 x 10⁸ m/s

λ is the wavelength of the electromagnetic wave

Since the speed of light is constant, we can conclude that the energy of the electromagnetic wave is directly proportional to its frequency and inversely proportional to its wavelength.

Therefore, the correct option for direct proportionality is FREQUENCY

You can do only number 1 only

Answers

For 1000 seconds , a current of 0.1 A flows so as to transfer charge of 100C

After rearranging the formula Q = It, to find for time, the new formula would be:
t = Q / I
From question:
Q = 100C
I = 0.1A

Therefore, time, t = 100 / 0.1 = 1000 s
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