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kenny6666 [7]
4 years ago
14

A circular jogging track forms the edge of a circular lake that has a diameter of 2 miles. Johanna walked once around the track

at the average rate of 3 miles per hour. If t represents the number of hours it took Johanna to walk completely around the lake, which of the following is a correct statement?(A) 0.5< t < 0.75 (B) 1.75< t < 2.0 (C) 2.0 < t < 2.5 (D) 2.5 < t < 3.0 (E) 3 < t < 3.5
Physics
1 answer:
Taya2010 [7]4 years ago
7 0

Answer:

The number of hours is 2.1.

(c) is a correct statement.

Explanation:

Given that,

Diameter = 2 miles

Average rate = 3 miles/hr

We need to calculate the time

Using formula of average rate

Average\ rate =\dfrac{Total\ distance}{Total\ time}

Put the value into the formula

3=\dfrac{2\pi\times r}{t}

t=\dfrac{6.28}{3}

t = 2.1\ hr

2.1 lies between 2.0 and 2.5.

Hence, The number of hours is 2.1.

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Which would take more force to stop in 10 seconds: an 8.0-kilogram ball rolling in a straight line at a speed of 0.2 m/s or a 4.
aliina [53]

You can do this two ways:

1).  Whatever kinetic energy the rolling ball has is the amount
of energy you have to absorb in order to stop it.

2).  Whatever momentum the rolling ball has is the amount of
momentum you have to provide in the other direction to cancel it.

Since you asked about force and time, we sense 'impulse' in the
air, and we know that impulse is exactly a change in momentum.
So let's use #2 and talk about momentum and impulse.

Impulse = (force) x (time)

Momentum of a moving object is  (mass) x (speed) .


-- Momentum of the first ball:  (8 kg) x (0.2 m/s) = 1.6 kg-m/s

Impulse required to stop it = 1.6 kg-m/s

         (force) x (10 sec) = 1.6

         Force required  =  1.6 / 10  =  0.16 Newton .


-- Momentum of the second ball:  (4 kg) x (1 m/s) = 4 kg-m/s

Impulse required to stop it =  4 kg-m/s

         (force) x (10 sec) = 4

         Force required  =  4 / 10  =  0.4 Newton .

You need more force o stop the second ball.  Although its mass
is only 1/2 the mass of the 8kg ball, it's moving 5 times as fast,
and has 2.5 times the momentum of the bigger ball. 
So you need 2.5 times as much impulse to stop it.
If you're going to push on each ball for the same length of time,
then you need to push 2.5 times as hard on the smaller ball in
order to stop it.

6 0
3 years ago
Read 2 more answers
A force of 210 N is applied to an object and the object accelerates at 14m/s2. Determine the mass of the object in kg.
lisabon 2012 [21]

Answer:

15 kg

Explanation:

F = m*a

F/a = m

210/14 = 15 kg

7 0
3 years ago
More recent findings of children with exceptionally high IQs _
Alenkasestr [34]

Answer:

Explanation:

Researchers and educators differ in how they define gift-

edness. Traditionally, researchers have defined giftedness

as high general intelligence as measured by a high global

IQ score (Hollingwort

Exceptionally intelligent students (hereafter referred to

as gifted students) face a variety of problems in ordinary

classrooms. They often are ostracized as being different

and weird and are labeled as nerds and geeks (Silverman,

1993a, 1993b). In addition, they face the problem of

boredom due to lack of an appropriate level of challenge

(Csikszentmihalyi, Rathunde, & Whalen, 1993; Gross,

1993). Teachers often make little accommodation to the

needs of these children, and many teachers have little

or no special training in how to teach such exceptional

children

5 0
3 years ago
A car going 50 mph accelerates to pass a truck. Five seconds later the car is
Alex

The vehicle accelerates at 2.648 m/s².

We have:

Initial velocity, u = 50 miles per hour = 22.352 m/s

final velocity, v = 80 miles per hour = 35.762 m/s

Time, t = 5 seconds

The time in hours is:

t = 5 seconds

Now, the acceleration of the car can be calculated using the formula:

v = u + at

35.762 = 22.352 + a(5)

a(5) = 30

a = 2.682 m/s²

From the calculations above, the acceleration of the car is 2.682 m/s².

Ler more about acceleration here:

brainly.com/question/605631

#SPJ9

3 0
2 years ago
A 0.0434-m3 container is initially evacuated. Then, 4.19 g of water is placed in the container, and, after some time, all of the
adell [148]

Answer:

P =18760.5 Pa

Explanation:

Given that

Volume ,V= 0.0434 m³

Mass ,m= 4.19 g = 0.00419 kg

T= 417 K

If we assume that water vapor is behaving like a ideal gas ,then we can use ideal gas equation

Ideal gas equation    P V = m R T

p=Pressure ,V = Volume ,m =mass

T=Temperature ,R=Universal gas constant

Now by putting the values

P V = m R T

For water R= 0.466 KJ/kgK

P x 0.0434 = 0.00419 x 0.466 x 417

P =18.7605 KPa

P =18760.5 Pa

Therefore the answer is 18760.5 Pa

6 0
4 years ago
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