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Nesterboy [21]
2 years ago
15

Which forces are acting on the student and the skateboard in the instant in which they are pushing off the wall? (Select all tha

t apply)
A. The force of the student pushing the wall
B.The force of gravity on the skateboard and the student
C.The force of the wall pushing on the student
D. The force of the floor pushing on the skateboard and the student
or E. Select all of the above
Physics
2 answers:
diamong [38]2 years ago
7 0
E all of the answers above correlate to the student and his skateboard
Vinil7 [7]2 years ago
5 0
Answer

E. Select all of the above

Explanation

They are all true
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You wish to cool a 1.83 kg block of tin initially at 88.0°C to a temperature of 57.0°C by placing it in a container of kerosene
uranmaximum [27]

Answer:

0.273 liters are needed to accomplish this task without boiling.

Explanation:

The minimum boiling point of kerosene is 150\,^{\circ}C. According to this question, we need to determine the minimum volume of liquid such that heat received is entirely sensible, that is, with no phase change.

If we consider a steady state process and that energy interactions with surrounding are negligible, then we get the following formula by the Principle of Energy Conservation:

\rho_{k}\cdot V_{k}\cdot c_{k}\cdot (T-T_{k,o}) = m_{t}\cdot c_{t}\cdot (T_{t,o}-T) (1)

Where:

\rho_{k} - Density of kerosene, measured in kilograms per cubic meter.

V_{k} - Volume of kerosene, measured in cubic meters.

c_{k}, c_{t} - Specific heats of the kerosene and tin, measured in joule per kilogram-Celsius.

T_{k,o}, T_{t,o} - Initial temperatures of kerosene and tin, measured in degrees Celsius.

T - Final temperatures of the kerosene-tin system, measured in degrees Celsius.

Please notice that the block of tin is cooled at the expense of the temperature of the kerosene until thermal equilibrium is reached.

From (1), we clear the volume of kerosene:

V_{k} = \frac{m_{t}\cdot c_{t}\cdot (T_{t,o}-T)}{\rho_{k}\cdot c_{k}\cdot (T-T_{k,o})}

If we know that m_{t} = 1.83\,kg, c_{t} = 218\,\frac{J}{kg\cdot ^{\circ}C}, T_{t,o} = 88\,^{\circ}C, T_{k,o} = 24.0\,^{\circ}C, T = 57\,^{\circ}C, c_{k} = 2010\,\frac{J}{kg\cdot ^{\circ}C} and \rho_{k} = 820\,\frac{kg}{m^{3}}, then the volume of the liquid needed to accomplish this task without boiling is:

V_{k} = \frac{(1.83\,kg)\cdot \left(218\,\frac{J}{kg\cdot ^{\circ}C} \right)\cdot (88\,^{\circ}C-57\,^{\circ}C)}{\left(820\,\frac{kg}{m^{3}} \right)\cdot \left(2010\,\frac{J}{kg\cdot ^{\circ}C} \right)\cdot (57\,^{\circ}C-24\,^{\circ}C)}

V_{k} = 2.273\times 10^{-4}\,m^{3}

V_{k} = 0.273\,L

0.273 liters are needed to accomplish this task without boiling.

3 0
3 years ago
Juan is receiving bills from the hospital even though his insurance company said his procedure would be covered in full. What st
BaLLatris [955]

==> Jot down notes before and after making each call, and avoid calling during business hours when people are busy.

==> Save all emails and bills, and follow up to make sure people did what they said they would do.

5 0
2 years ago
How long should a spring be stretched for it to store 45 J of energy? The force constant of the spring is
ELEN [110]

Answer:

x = 0.4 m

Explanation:

When a spring is stretched from its equilibrium position. Some energy is stored in the spring. This energy is called the elastic potential energy of the spring. The formula used to calculate the magnitude of this stored energy is given as follows:

P.E = (1/2)kx²

where,

P.E = Elastic Potential Energy Stored in the spring = 45 J

k = Spring Constant = 540 N/m

x = amount of stretching = ?

Therefore,

45 J = (1/2)(540 N/m)x²

x² = (45 J)(2)/(540 N/m)

x = √(0.167 m²)

<u>x = 0.4 m</u>

5 0
3 years ago
To impress his friends while riding on a carnival
s344n2d4d5 [400]

Answer:

B. decreases while his angular speed remains  unchanged.

Explanation:

His angular speed will always be the same as the wheel's angular speed, which remains constant as it's in uniform motion. As for linear speed, which is defined as the product of angular speed and distance r to the center of rotation, and his distance to center is decreasing, his linear speed must be decreasing as well.

8 0
3 years ago
Match the term with each description:
Alex_Xolod [135]

Answer:

An acid is a compound that increases hydrogen ions (H+) when it is dissolved in a solution.

all I got

4 0
3 years ago
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