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4 years ago

A cross-country skier can complete a 7.5 km race in 45 min. What is the skier’s average speed?

Physics

2 answers:

Triss [41]4 years ago

8 0

Answer

2.7778 m/s

Explanation

Speed is rate of change of distance with time.

It is the distance covered in a unit time. SI units of speed in m/s. Other units are Km/h, knots e.t.c

Average speed = (total distance covered) / (total time taken)

= 7.5 Km / 45 Min

= 1/6 Km/Min

Or,

7.5Km = (7.5 × 1000) m = 7500 m

45 min = 45 × 60 2700 seconds

Average speed = 7500/2700

= 2.7778 m/s

Alecsey [184]4 years ago

7 0

To calculate for the average speed, we simply divide the total distance covered by the time it takes to travel that distance. In this case, we simply divide 7.5 km with 45 min. Therefore, the skier's average speed is 0.1667 km/min. Hope this helps.

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Suppose that the dipole moment associated with an iron atom of an iron bar is 2.8 × 10-23 J/T. Assume that all the atoms in the

masya89 [10]

To solve this exercise it is necessary to apply the equations related to the magnetic moment, that is, the amount of force that an image can exert on the electric currents and the torque that a magnetic field exerts on them.

The diple moment associated with an iron bar is given by,

$\mu = \alpha *N$

Where,

$\alpha =$ Dipole momento associated with an Atom

N = Number of atoms

$\alpha$ y previously given in the problem and its value is 2.8*10^{-23}J/T

$L = 5.8cm = 5.8*10^{-2}m$

$A = 1.5cm^2 = 1.5*10^{-4}m^2$

The number of the atoms N, can be calculated as,

$N = \frac{\rho AL}{M_{mass}}*A_n$

Where

$\rho =$ Density

$M_{mass} =$ Molar Mass

A = Area

L = Length

$A_n =$ Avogadro number

$N = \frac{(7.9g/cm^3)(1.5cm)(5.8cm^2)}{55.9g/mol}(6.022*10^{23}atoms/mol)$

$N = 7.4041*10^{23}atoms$

Then applying the equation about the dipole moment associated with an iron bar we have,

$\mu = \alpha *N$

$\mu = (2.8*10^{-23})*(7.4041*10^{23})$

$\mu = 20.72Am^2$

PART B) With the dipole moment we can now calculate the Torque in the system, which is

$\tau = \mu B sin(90)$

$\tau = (20.72)(2.2)$

$\tau = 45.584N.m$

Note: The angle generated is perpendicular, so it takes 90 ° for the calculation made.

3 0

3 years ago

The energy your body gets from food is originally provided by which nuclear

Naily [24]

Answer:

Nuclear Fusion

Explanation:

The process releases energy because the total mass of the resulting single nucleus is less than the mass of the two original nuclei. The leftover mass becomes energy.

4 0

3 years ago

A car speeding down the highway honks its horn, which has a frequency 392 Hz, but a resting bystander hears the frequency 440 Hz

Natali [406]

Answer:

37.42 m/s

Explanation:

We know that apparent frequency, $\bar f$ is given by

$\bar f=f\frac {V}{V-V_s}$ where f is the given frequency in this case 392, V is the speed of sound in air which is given as 343 and $V_s$ is the speed of car which is unknown, \bar f is given as 440 Hz