PHYSICS HIGH SCHOOL

"At a cross-country track meet, Alicia ran 8 mph for the first part of the race, then increased her speed to 12 mph for the second part. If the race was 21 miles long and Alicia finished in 2 hours, how far did she run at the faster pace?"

Answers

Answer 1

Answer:

Alicia ran 15 miles at the faster pace.

Formulating the equations:

Let Alicia run with the speed of 12mph for A hours and with the speed of 8mph for B hours.

Total distance is 21 miles, so we can make the first equation as:

12A + 8B = 21 .............(i)

Now the total time taken is 2 hours, which means:

A + B = 2 ..............(ii)

Now multiply equation (ii) by 8 and subtract from equation (i)

then we get, 4A = 5

A = 5/4 hours

So Alicia run at the speed of 12mph for 5/4 hours, total distance covered is:

d = 12 × 5/4

d = 15 miles

Learn more about speed and distance:

brainly.com/question/12759408?referrer=searchResults

Answer 2

Answer:

Answer:

15 miles

Explanation:

Alicia's speed in the first part of the race is:

$v_1 = (d_1)/(t_1)=8 mph$

where $d_1$ is the length of the first part and $t_1$ the time taken to cover this part.

Alicia's speed in the second part of the race is:

$v_2 = (d_2)/(t_2)=12 mph$

where $d_2$ is the length of the second part and $t_2$ the time taken to cover this part.

The total length of the race is

$d=d_1 +d_2 = 21 mph$

And the total time taken by Alicia to complete the race is

$t=t_1 + t_2 = 2 h$

We have in total 4 equations with 4 unknown quantities. From the first 2 equations we find:

$d_1 = 8t_1\nd_2 = 12 t_2$

And substituting into the second group of equations:

$8t_1 + 12t_2 =21\nt_1 + t_2 = 2$

Calling A the first equation and B the second equation, if we compute (A-8B) we get:

$4t_2 = 5 \rightarrow t_2 = 1.25h$

And so

$t_1 = 2-t_2 = 0.75 h$

So Alicia runs for 1.25 hours at 12 mph (second part of the race). Therefore, the distance travelled during this part is:

$d_2 = v_2 t_2 = 12 \cdot 1.25 = 15 mi$

Therefore the answer is 15 miles.

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Yello light on a red object, the object appears what color ?

1. Read each description below. Choose the force diagram (free-body diagram) that best represents the description. The forces are acting on the object in red type. You may neglect the effects of air resistance. A. Mindy's Christmas tree ornament hangs motionless on a tree.
B. Corey's Christmas tree ornament is falling to the floor.
C. A ball thrown by Ginger is moving upward through the air.
D. A ball dropped by Melissa is falling downward toward the floor.
E. Matt's book is motionless on a table.
F. A ball that was thrown upward by Yvonne is at the top of its path.

For each statement, please choose a diagram representing the force on the object. (Diagrams are in the attachment)

Answers

A. Mindy's Christmas tree ornament hangs motionless on a tree. --- Diagram C
B. Corey's Christmas tree ornament is falling to the floor. --- Diagram A
C. A ball thrown by Ginger is moving upward through the air. --- Diagram B
D. A ball dropped by Melissa is falling downward toward the floor. --- Diagram A
E. Matt's book is motionless on a table. --- Diagram C
F. A ball that was thrown upward by Yvonne is at the top of its path --- Diagram A.

Final answer:

Free-body diagrams are tools to visualize external forces on an object, drawn as a point. Each scenario given (hanging ornament, falling ornament, moving and dropped balls, book on a table, and ball at top of its path) will have a unique diagram with forces like gravity, tension, and normal force labeled as vectors, and x/y components shown if necessary.

Explanation:

In physics, a free-body diagram is a graphical representation used to visualize the forces acting on an object. To correctly create a free-body diagram, follow these steps:

Draw the object as a point, especially when considering it as a particle.
Label all the external forces acting on the object with vector arrows.
Resolve each force into its x and y components if necessary for analysis.
Create separate diagrams for each object if multiple objects are involved.

Each scenario provided in the question will have a different free-body diagram:

Mindy's Christmas tree ornament: It's stationary, with two forces in balance: gravitational force (weight) pulling down and the tension in the string pulling up.
Corey's Christmas tree ornament: Only one force, gravitational force, is acting on it as it falls.
Ginger's ball moving upward: Two forces here - gravitational force pulling down and the initial upward force while it moves up.
Melissa's dropped ball: Similar to B, only gravitational force acts on it.
Matt's book on a table: Gravitational force pulls it down while the normal force from the table supports it from below.
Yvonne's ball at the top of its path: Though motionless at this instant, the only force acting on it is gravity.

Note, while drawing a free-body diagram, do not include net forces or internal forces.

In order to increase thermal energy, the temperature must ___________.a.
increase
c.
remain the same
b.
decrease
d.
it cannot be determined

Answers

Answer: Option (a) is the correct answer.

Explanation:

Energy obtained by an object due to the motion of particles that are present within the object is known as thermal energy.

So, when we increase the temperature of a substance then its molecules tend to gain kinetic energy. Because of this molecules will start to move from their initial position and hence, there will be more number of collisions between the molecules.

As a result, there will be increase in thermal energy of the substance.

Thus, we can conclude that in order to increase thermal energy, the temperature must increase.

In order to increase thermal energy, the temperature must increase

What is the best angle for maximum height and air time? explain why you think this is so.

Answers

Answer: 90 degrees

Explanation:

The projectile will have the greatest air time and height when the launch is the most vertical. At 90 degrees, the launch is all vertical.

A drowsy cat spots a flowerpot that sails first up and then down past an open window. The pot is in view for a total of 0.66 s, and the top-to-bottom height of the window is 1.80 m. How high above the window top does the flowerpot go? (Assume that in both sailing upward and then falling downward, the flowerpot is seen to span the full vertical height of the window.)

Answers

Answer:

Height covered after crossing window top = 0.75 m

Explanation:

In the question,

The height of the window pane = 1.8 m

Time for which the flowerpot is in view = 0.66 s

So,

The time for which it was in view while going up is = 0.33 s

Time for which it was in view while going down = 0.33 s

So,

Let us say,

The initial velocity of the flowerpot = u m/s

So,

Using the equation of the motion,

$s=ut+(1)/(2)at^(2)\n1.8=u(0.33)-(1)/(2)(9.8)(0.33)^(2)\n1.8=0.33u-0.5336\n0.33u=2.33\nu=7.07\,m/s$

So,

Velocity at the top of the window pane is given by,

$v=u+at\nv=7.07-(9.8)(0.33)\nv=3.836\,m/s$

Now,

Let us say the height to which the flowerpot goes after crossing the window pane is = h

So,

Using the equation of motion,

$v^(2)-u^(2)=2as\n(0)^(2)-(3.836)^(2)=2(-9.8)h\nh=(14.714)/(19.6)\nh=0.75\,m$

Therefore, the height covered by the flowerpot after window is = 0.75 m

Calculate the average speed (in km/h) of a car stuck in traffic that drives 12 kilometers in 2 hours

Answers

it is distance divide by time will get you speed
12/2 = 6 km/h
hope this helps

A wave has a period of 2 seconds and a wavelength of 4 meters.Calculate its frequency and speed.

Answers

f=l/t
f=4/2
f=2m/s

Hope this helps

Answer:

f = 0.5 Hz

v = 8 m/s

Explanation:

f = 1/T

f = 1/(2) = 0.5 Hz

v = λf

v = (2)(4) = 8 m/s

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