Question

1. Rubbing your hands together warms them by converting work into thermal energy. If a woman rubs her hands back and forth for a total of 16 rubs, at a distance of 7.50 cm per rub, and with a frictional force of 40.0 N, what is the temperature increase in degrees Celsius? The mass of tissue warmed is only 0.100 kg, mostly in the palms and fingers. ____ °C.

Answer #1

Given:

The frictional force, F = 40.0 N

Number of rubs, N= 16

Distance covered per rub, d = 7.50 cm = 0.075 m

Total distance covered in 16 rubs, D = 0.075 × 16 = 1.20 m

mass of the tissues warmed, m = 0.100 kg

Now,

Work done, W = Force × Displacement

W = 40N × 1.20m = 48 J

Now,

Work done is the change in heat

W = ΔQ = 48 J

also,

ΔQ = mCΔT

where, C is the specific heat

for human tissue, C = 3500 J/kg°C

thus,

48 J = 0.1 × 3500 × ΔT

ΔT= 48 / (350)

or

ΔT = 0.1371°C

the temperature increase in degrees Celsius is =
0.1371°C |

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Rubbing your hands together warms them by converting work into
thermal energy. If a woman rubs her hands back and forth for a
total of 10 rubs a distance of 7.50 cm each and with a frictional
force averaging 50.0 N, what is the temperature increase? The mass
of tissue warmed is only 0.100 kg, mostly in the palms and
fingers.
_________

Rubbing your hands together warms them by converting work into
thermal energy. If a woman rubs her hands back and forth for a
total of 20 rubs, at a distance of 7.50 cm per rub, and with an
average frictional force of 40.0 N, what is the temperature
increase? The mass of tissues warmed is only 0.100 kg, mostly in
the palms and fingers.
They use the formula Q=NFd
I do not understand this formula or its derivation. It is...

rubbing your hands together warms them by completing
work into thermal energy. If a woman rubs her hands back-and-forth
for a total of 20 rubs, at a distance of 7.50 cm per rub, and with
an average frictional force of 40.0N, what is the temperature
increase? The mass of tissues warmed up is only 0.100 kg, mostly in
the palms and fingers.

If a woman rubs her hands back and forth for a total of 20 rubs,
at a distance of 5.3 cm per rub, and with an average frictional
force of 32.3 N, what is the temperature increase? The mass of
tissues warmed is only 0.104 kg, mostly in the palms and fingers.
Use a specific heat of 3500 J/kgºC.

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