. Alpha-emitting substances, such as radon gas, can be a serious health hazard only if . their radiation strikes the skin they are inhaled or eaten exposure to them is external

They are inhaled or eaten

Explanation:

Radioactivity can be defined as the process in which an unstable atomic nucleus spontaneously emits ionizing radiation and charge particles. This eventually results in the formation of an energetically stable atomic nucleus.

Examples of radioactive elements are Uranium, Polonium, Thorium, Radon, etc. The radiation emitted during this process is classified as;

1. Alpha radiation (α).

2. Beta radiation (β).

3. Gamma radiation (G).

Alpha-emitting substances, such as radon gas, can be a serious health hazard only if they are inhaled or eaten. Alpha-emitting substances compared to other radiation has very short-range particle and as such cannot penetrate the human skin or body.

less than one you can't create energy

the tires are rotating at 0.434 rpmlinear speed=45 m/sdiameter=0.550 mradius=0.275 mnow v= rωω= v/rω=45/0.275ω=163.6 rad/sω=163.6 rad/s (1rev/2π rad) (60s/1m)ω=1563 rpm