By using Ohm's law, we can find what should be the resistance of the wire, R:

Then, let's find the cross-sectional area of the wire. Its radius is half the diameter,

So the area is

And by using the resistivity of the Aluminum,

, we can use the relationship between resistance R and resistivity:

to find L, the length of the wire:
The density of sample is 5 g/cm3
Given:
volume of sample = 20 cm3
mass of sample = 100 grams
To Find:
density of sample
Solution: Density is the measure of how much “stuff” is in a given amount of space. For example, a block of the heavier element lead (Pb) will be denser than the softer, lighter element gold (Au). A block of Styrofoam is less dense than a brick. It is defined as mass per unit volume
density = mass/volume
d = 100/20
d = 5 g/cm3
So, density of sample is 5 g/cm3
Learn more about Density here:
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Complete Question
Q. Two go-carts, A and B, race each other around a 1.0km track. Go-cart A travels at a constant speed of 20m/s. Go-cart B accelerates uniformly from rest at a rate of 0.333m/s^2. Which go-cart wins the race and by how much time?
Answer:
Go-cart A is faster
Explanation:
From the question we are told that
The length of the track is 
The speed of A is 
The uniform acceleration of B is 
Generally the time taken by go-cart A is mathematically represented as
=> 
=> 
Generally from kinematic equation we can evaluate the time taken by go-cart B as

given that go-cart B starts from rest u = 0 m/s
So

=>
=>
Comparing
we see that
is smaller so go-cart A is faster
Explanation:
given,
mass of one planet (m1)=2*10^23 kg
mass of another planet (m2)=5*10^22kg
distance between them(d)=3*10^16m
gravitational constant(G)=6.67*10^-11Nm^2kg^-2
gravitational force between them(F)=?
we know,
F=Gm1m2/d^2
or, F=6.67*10^-11*2*10^23*5*10^22/(3*10^16)^2
or, F=6.67*2*5*10^-11+23+22/3*3*10^32
or, F=66.7*10^34/9*10^32
or, F=7.41*10^34-32
•°• F=7.41*10^2
thus, the gravitational force between them is 7.14*10^2