Use of electromagnetic because it moves very faster than others for example xrays theynar very very slow so that not It it is d.
The atomic number gives you the number of protons element x has. Since the mass of protons and neutrons are almost similar(around 1 amu), the mass number can be thought of as the sum of protons and neutrons. so if element x whose atomic number is 40 has a mass number of 82, then we know that 42 of those must be neutrons.
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A.
Since the can was launched from ground level, we know that its trajectory forms a symmetrical, parabolic shape. In other words, the time taken for the can to reach the top is the same as the time it takes to fall down.
Thus, the time to its highest point:

Now, we can determine the velocity at which the can was launched at using the following equation:

In this instance, we are going to look at the VERTICAL component of the velocity, since at the top of the trajectory, the vertical velocity = 0 m/s.
Therefore:

***vsinθ is the vertical component of the velocity.
Solve for 'v':

Now, recall that:

Plug in the expression for velocity:

B.
We can use the same process as above, where T' = 2T and Th = T.

C.
The work done in part B is 4 times greater than the work done in part A.

Answer:
Emphasis on public safety can surely reduce the risk for various groups of population
1. Proper education and training must be provided to make them aware of the risks and how they can manage those risks.
2. Proper rules and regulation must be made and strictly followed for example traffic rules so as to avoid accidents.
3. Disaster management teams should to formed to ensure minimal loss of humans and resources during any natural calamity.
4.Eradication of poverty and illiteracy should be priority so as to ensure people focus on more important issues in life rather than involve themselves in trivial things.
Explanation: