Answer:
5 ) The mass, 6) with lubrication and using surfaces that are not rough
Explanation:
5) If two bodies are held regardless of their densities and can be combined by some chemical or physical process, the only physical property to be modified will be the mass of the resulting body.
8)
Friction depends on the contact between two surfaces and when a body has a relative motion with respect to a contact surface. In order to reduce friction the contact surface must be lubricated, also the friction depends on the coefficient of friction between surfaces and the normal force exerted by the surface parallel to the area of contact with the body. Mathematically it can be expressed with the following equation.
![F_{f} = u*N\\where:\\u = friction coefficient\\N = normal force [Newtons]\\F_{f}= friction force [Newtons]](https://tex.z-dn.net/?f=F_%7Bf%7D%20%3D%20u%2AN%5C%5Cwhere%3A%5C%5Cu%20%3D%20friction%20coefficient%5C%5CN%20%3D%20normal%20force%20%5BNewtons%5D%5C%5CF_%7Bf%7D%3D%20friction%20force%20%5BNewtons%5D)
Answer:

Explanation:
The resistance of a wire is given by the equation:

where
is the resistivity of the material
L is the length of the wire
A is the cross-sectional area of the wire
In this problem, we have a wire of platinoid, whose resistivity is

The length of the wire is
L = 7.0 m
And its radius is
, so the cross-sectional area is

Solving for R, we find the resistance of the wire:

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