1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
SSSSS [86.1K]
3 years ago
13

In April 1974, Steve Prefontaine completed a 10 km race in a time of 27 min, 43.6 s. Suppose "Pre" was at the 8.13 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 8.13 km mark was the same as his overall average speed up to that time.
Physics
1 answer:
SOVA2 [1]3 years ago
5 0

Answer:0.084 m/s^2

Explanation:

Given

Total time=27 min 43.6 s=1663.6 s

total distance=10 km

Initial distance d_1=8.13 km

time taken=25 min =1500 s

initial speed v_1=\frac{8.13\times 1000}{25\times 60}=5.6 m/s

after 8.13 km mark steve started to accelerate

speed after 60 s

v_2=v_1+at

v_2=5.6+a\times 60

distance traveled in 60 sec

d_2=v_1\times 60+\frac{a60^2}{2}

d_2=336+1800 a

time taken in last part of journey

t_3=1663.6-1560=103.6 s

distance traveled in this time

d_3=v_2\times t_3

d_3=\left ( 5.6+a\times 60\right )103.6

and total distance=d_1+d_2+d_3

10000=8.13\times 1000+336+1800 a+\left ( 5.6+a\times 60\right )103.6

1870=336+1800 a+\left ( 5.6+a\times 60\right )103.6

a=0.084 m/s^2

You might be interested in
A car travels at a speed of 55 km/hr and slows down to 10 km/hr in 20 seconds. What is the acceleration?
WITCHER [35]

Answer:

b

Explanation:

3 0
3 years ago
Read 2 more answers
Kelli weighs 425 N, and she is sitting on a playground swing that hangs 0.36 m above the ground. Her mom pulls the swing back an
kodGreya [7K]

Answer:

V = 3.54 m/s

Explanation:

Using the conservation of energy:

E_i = E_f

so:

wh = \frac{1}{2}mV^2

where w is te weigh of kelly, h the distance that kelly decends, m is the mass of kelly and V the velocity in the lowest position.

So, the mass of kelly is:

m = 425N/9.8 = 43.36 Kg

and h is:

h = 1m-0.36m =0.64m

then, replacing values, we get:

(425N)(0.64m) = \frac{1}{2}(43.36kg)v^2

Solving for v:

V = 3.54 m/s

7 0
3 years ago
Explain the conversion of energy in a roller coaster. Explain how energy is converted
tatuchka [14]
As the rollercoaster goes up. kinetic energy changes to gravitational potential energy. When it moves back down, gpe changes back to ke.
5 0
3 years ago
How many energy levels do the electrons occupy for a neutral Oxygen atom? *
Sophie [7]

Answer:

The neutral state of an atom is when it's net charge is zero; that is, the number of protons equals the numbers of electrons. Oxygen is the eighth element in the periodic table, with the symbol O. This means that it has eight electrons in its neutral state. Since it is neutral, it also has eight protons!

6 0
2 years ago
A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows
anastassius [24]

Answer:

In the vertical direction the acting forces are the normal force and the weight of the bobsleder plus the sled. In the horizontal direction the acting force is the friciton force.

Explanation:

Hi there!

Please, see the attached figure for a graphic representation of the forces acting on the sled after the bobsleder jumped in.

In the vertical direction, the acting forces are the normal force (N) and the weight of the sled plus the bobsledder (W).

Since the sled is not being accelerated in the vertical direction, the sum of forces in that direction is zero:

∑Fy = W + N = 0 ⇒ W = N

The weight is calculated as follows:

W = (mb + ms) · g

Where:

mb = mass of the bobsleder.

ms = mass of the sled.

g = acceleration due to gravity.

In the horizontal direction the only acting force is the friction force (Fr). The friction force is calculated a follows:

Fr = N · μ

Where:

N = normal force.

μ = kinetic friction coefficient.

Since N = W = (mb + ms) · g

Fr = (mb + ms) · g · μ

If we want to find the acceleration of the sled after the bobsleder jumps in, we can apply Newton's second law:

∑F = m · a

Where "a" is the acceleration and "m" is the mass of the object (in this case, the mass of bobsleder plus the mass of the sled).

∑F = Fr =  (mb + ms) · g · μ =  (mb + ms) · a

(mb + ms) · g · μ =  (mb + ms) · a

Solving for "a":

g · μ = a

3 0
3 years ago
Other questions:
  • Need help on question b
    7·1 answer
  • Calculate the wavelengths of the first five members of the Lyman series of spectral lines, providing the result in units Angstro
    6·1 answer
  • Mr. Llama walked from his house to the bus stop. The bus stop is 2 miles from his house. He returned back to his house from the
    15·1 answer
  • Mechano, the evil robot cat, has captured the mous
    6·1 answer
  • my question is about a cupcake recipe and there asking me about a 7-digit code with no spaces and to me that question was pretty
    8·1 answer
  • during a dodge ball game a student throw a ball at another player what forces act on the ball as it flie through the air
    14·1 answer
  • Kamala puts on inline skates and stands facing a wall. When she pushes against the wall, she rolls backward. Why does pushing ha
    13·2 answers
  • Which of the following could be used to sterilize plastic petri plates in a plastic wrapper? A) ultraviolet radiation B) microwa
    11·1 answer
  • What is force ? <br>question for spammers hehe..​
    5·2 answers
  • Some jovian planets give off more energy than they receive because of
    13·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!