Varies: There is no specific dangerous heart rate during exercise. How fast your heart beats with exercise depends on a number of factors, especially your conditioning. If you are healthy, a heart reate in the 170's or even higher may be ok and tolerated.
Motion sickness caused by video games, sometimes called simulator sickness, is caused when there is a disconnect between what your eyes are seeing and what your body is feeling.
Acute mountain sickness is caused by reduced air pressure and lower oxygen levels at high altitudes. The faster you climb to a high altitude, the more likely you will get acute mountain sickness. You are at higher risk for acute mountain sickness if: You live at or near sea level and travel to a high altitude.