Please elaborate more on your question so I can help you
The answer is control variable
Answer:B
Explanation:
Given
mass of Sled is m
another package of mass m is thrown on it
Suppose u be the initial velocity of sled
conserving momentum
where v is the final velocity
Initial kinetic energy 
Final Kinetic Energy
Final Kinetic Energy
Final kinetic Energy is half of initial
Answer:
Density is defined as:
Density = Mass/Volume
Now, density is an intensive property, this means that if you have 10 grams of a given material or 1000 grams of the same material, in both cases you will find the same density.
Then a roll of 50 pennies has the same density that a single penny.
The measures of a single penny are:
Mass = 2.5 g
Thickness = 1.52 mm
Radius = 9.525 mm
The coin is a cylinder, and the volume of a cylinder is:
V = pi*r^2*h
where:
pi = 3.14
r = radius = 9.525mm
h = thikness = 1.52mm
The volume is:
V = 3.14*(9.525mm)^2*1.52mm = 433.015 mm^3
The density will be:
D = 2.5g/433.015mm^3 = 0.00577 g/mm^3
The magnetic force exerted by a field E to a charge q is given by F=Eq. In this case, F=4.30*10^4*(6.80mu C). 1mu C=10^-6C, so F=4.30*6.80=10^-2=0.29N. The direction is in the x direction, the direction that the field is applied because the charge is positive.
