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melisa1 [442]
3 years ago
15

Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a to

tal of 18 rubs, at a distance of 7.16 cm per rub, and with an average frictional force of 48 N, what is the temperature increase? The mass of tissues warmed is only 0.1 kg, mostly in the palms and fingers.
Physics
1 answer:
KATRIN_1 [288]3 years ago
6 0

Answer:

0.178 °C

Explanation:

Given:

The frictional force, F = 48 N

Number of rubs, n = 18

Distance covered per rub, d = 7.16 cm = 0.0716 m

Total distance covered in 18 rubs, D = 0.0716 × 18 = 1.288 m

mass of the tissues warmed, m = 0.1 kg

Now,

Work done, W = Force × Displacement

W = 48 × 1.288 = 61.8624 J

Now,

Work done is the change in heat

W = ΔQ = 61.8624 J

also,

ΔQ = mCΔT

where, C is the specific heat

for human tissue, C = 3470 J/kg°C

thus,

61.8624 J = 0.1 × 3470 × ΔT

or

ΔT = 0.178 °C

Hence, the change in temperature is 0.178 °C

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Answer:

a) 0.303 s b) 6.77 m/s c) - 2.97  m/s d) 7.39 m/s

Explanation:

horizontal distance travel = 2.050 m, vertical distance travel = 0.45 m

Using equation of linear motion

Sy = Uy t + 1/2 gt² Uy is the inital vertical component of the velocity, t is the time taken for the vertical motion in seconds, and S is the vertical distance traveled, taken downward vertical motion as negative

-0.45 = 0 - 0.5 × 9.81×t²

0.45 / (0.5 × 9.81) = t²

t = √0.0917 = 0.303 s

b) horizontal distance traveled = horizontal velocity (Ux) × t

Ux = horizontal distance traveled / t = 2.050 / 0.303 = 6.77 m/s

c) Velocity in the vertical direction can be calculated using

Vy = Uy - gt where g is negative since initial U is zero

Vy = - 9.81 × 0.303 = - 2.97  m/s

d) the magnitude of the velocity = resultant of the the two velocity

using Pythagoras theorem

the magnitude of the velocity = √ ( 6.77² + 2.97²) = 7.39 m/s

at angle = tan^-1 ( 2.97 / 6.77) =  23.69⁰

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3 years ago
Being underinsured is one of the main reasons that some people are unable to get quality health care. Please select the best ans
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A person 1.8m tall stands 0.75m from a reflecting globe in a garden.
Maru [420]

Answer:

1. The image of the person is 1.41 m, virtual and formed at the back of the surface of the globe.

2. The person's image is 3.38 m tall.

Explanation:

From the given question, object distance, u = 0.75 m, object height = 1.8 m, radius of curvature of the reflecting globe, r = 8 cm = 0.08 m.

f = \frac{r}{2} = \frac{0.08}{2} = 0.04 m

1. The image distance, v, can be determined by applying mirror formula:

\frac{1}{f} = \frac{1}{u} + \frac{1}{v}

\frac{1}{0.04} = \frac{1}{0.75} + \frac{1}{v}

\frac{4}{100} - \frac{75}{100} = \frac{1}{v}

\frac{1}{v} = \frac{4 - 75}{100}

  = - \frac{71}{100}

⇒ v = -\frac{100}{71}

      = - 1.41 m

The image of the person is 1.41 m, virtual and formed at the back of the surface of the globe.

2.  \frac{image distance}{object distance} = \frac{image height}{object height}

  \frac{1.41}{0.75} = \frac{v}{1.8}

v = \frac{2.538}{0.75}

  = 3.384

v = 3.38 m

The person's image is 3.38 m tall.

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3 years ago
In order for a length of copper wire or a loop of copper wire to have a magnetic field, what must they have flowing through them
Nataliya [291]
Electricity.
When electricity flows through wire (such as a battery circuit) it creates a magnetic field around the wire.
6 0
3 years ago
In the Daytona 500 auto race, a Ford Thunderbird and a Mercedes Benz are moving side by side down a straightaway at 78.5 m/s. Th
Andrews [41]

Answer:

FT is 1020.6 meters (1640.6 meters - 620 meters) far from MB

Explanation:

First you have to consider that the Ford Thunderbird (FT) follows a rectilinear motion with varying acceleration, while Mercedez Benz (MB) has a constant velocity (no acceleration). So if you finde the time spent by FT in each section, and the distance, then you will find the distance for MB.

1) Vf² = Vi² + 2ad, where Vf: final velocity, Vi: ionitial velocity, a: acceleration and d: distance.

For the first portion  (0 m/s)² = (78.5 m/s)² + 2a(250 m) ⇒

-(78.5 m/s)² / 2(250m) = a ⇒ a = -12.3 m/s².

Now, you can find the corresponding time for this section with the following formule: Vf = Vi + at ⇒ 0 m/s = 78.5 m/s + (-12.3 m/s²) t

⇒ t= (-78.5 m/s)/ (-12.3 m/s²) ⇒ t= 6.4 seconds.

2) Then FT spent 5 seconds in the pit.

3) The the FT accelerates until reach 78.5 m/s again in a distance of 370 m.

Vf² = Vi² + 2ad ⇒ (78.5 m/s)² = (0 m/s)² + 2a(370 m)

⇒ (78.5 m/s)²/ 2(370 m) = a ⇒ a = 8.3 m/s²

Then, Vf = Vi + at ⇒ 78.5 m/s = 0 m/2 + (8.3 m/s²) t

⇒ (78.5 m/s)/(8.3 m/s²) = t ⇒ t = 9.5 seconds.

4) Summarizing, the FT moves 620 meters (250 + 370 mts) in 20.9 seconds ( 6.4 s + 5 s + 9.5 s).

5) During this time, MB moves

Velocity = distance/ time ⇒ Velocity x time = Distance

⇒ Distance = (78.5 m/s) x  (20.9 seconds) ⇒ Distance = 1640.6 meters

6) Finally, the FT is 1020.6 meters (1640.6 meters - 620 meters) far from MB

3 0
3 years ago
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