How much force does it take to accelerate a car mass 1750kg at 20m/s
1 answer:
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She can climb 0.92 m without losing weight.
<u>Explanation</u>:
Gravitational potential energy is the energy consisting of the product of mass, gravity and height.
1 cal = 4184 J
140 cal = 585760 J
Energy = 585760 J, m = 65.0 kg = 65000 g, Efficiency = 20 %
GPE = mgh
where m represents the mass
g represents the gravity,
h represents the height.
585760 = 65000 9.8
h
h = 0.92 m.
The text does not specify whether the resistance R of the wire must be kept the same or not: here I assume R must be kept the same.
The relationship between the resistance and the resistivity of a wire is
where
is the resistivity
A is the cross-sectional area
R is the resistance
L is the wire length
the cross-sectional area is given by
where r is the radius of the wire. Substituting in the previous equation ,we find
For the new wire, the length L is kept the same (L'=L) while the radius is doubled (r'=2r), so the new resistivity is
Therefore, the new resistivity must be 4 times the original one.
The relationship between the resistance and the resistivity of a wire is
where
A is the cross-sectional area
R is the resistance
L is the wire length
the cross-sectional area is given by
where r is the radius of the wire. Substituting in the previous equation ,we find
For the new wire, the length L is kept the same (L'=L) while the radius is doubled (r'=2r), so the new resistivity is
Therefore, the new resistivity must be 4 times the original one.