(a) A firewalker runs across a bed of hot coals without sustaining burns. Calculate the heat transferred by conduction into the sole of one foot of a firewalker given that the bottom of the foot is a 3.00-mm-thick callus with a conductivity at the low end of the range for wood and its density is 3 00 kg / m 3 . The area of contact is 25 .0 cm 2 , the temperature of the coals is 7 00 ° C , and the time in contact is 1.00 s. (b) What temperature increase is produced in the 25 .0 cm 3 of tissue affected? (c) What effect do you think this will have on the tissue, keeping in mind that a callus is made of dead cells?
(a) A firewalker runs across a bed of hot coals without sustaining burns. Calculate the heat transferred by conduction into the sole of one foot of a firewalker given that the bottom of the foot is a 3.00-mm-thick callus with a conductivity at the low end of the range for wood and its density is 3 00 kg / m 3 . The area of contact is 25 .0 cm 2 , the temperature of the coals is 7 00 ° C , and the time in contact is 1.00 s. (b) What temperature increase is produced in the 25 .0 cm 3 of tissue affected? (c) What effect do you think this will have on the tissue, keeping in mind that a callus is made of dead cells?
(a) A firewalker runs across a bed of hot coals without sustaining burns. Calculate the heat transferred by conduction into the sole of one foot of a firewalker given that the bottom of the foot is a 3.00-mm-thick callus with a conductivity at the low end of the range for wood and its density is
3
00
kg
/
m
3
. The area of contact is
25
.0
cm
2
, the temperature of the coals is
7
00
°
C
, and the time in contact is 1.00 s.
(b) What temperature increase is produced in the
25
.0
cm
3
of tissue affected?
(c) What effect do you think this will have on the tissue, keeping in mind that a callus is made of dead cells?
A = 45 kN
a = 60°
B = 20 kN
ẞ = 30°
Problem:M1.1
You and your friends are on an archaeological adventure and are trying to disarm an ancient trap to do so you
need to pull a log straight out of a hole in a wall. You have 1 rope that you can attach to the log and there are
currently 2 other ropes and weights attached to the end of the log. You
know the force and direction of the ropes currently attached are arranged
as shown below what is the magnitude and direction 'e' of the minimum
force you need to apply to the third rope for the force on the log to be in
direction of line 'a'? What is the resultant force in direction 'a'?
a
//////
//////
answer both questions
- 13-
3.
Shastri recalled reading that for an ideal transformer, "the ratio of the primary voltage to the
secondary voltage is equal to the ratio of the secondary current to the primary current."
Plan and design an experiment to investigate whether the statement above is true.
(8)
•
With the aid of a fully labelled circuit diagram, describe a procedure which can be used to
investigate whether the statement is true. The circuit diagram must include the following
components:
A variable AC voltage supply
•
AC voltmeters
•
AC ammeters
A transformer with adjustable turns ratio
Connecting wires
•
°
A load resistor
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