Question 17 Calculate the force exerted by the biceps to hold up
the forearm and a book whose mass m= 5.8 kg. The
pivot point is at the elbow joint.

Solution: holding up → rotational equilibrium;

Which influences tend to change the state of
rotational motion ?

the aurora is formed when charged particles emitted from the sun during a solar flare penetrate the earth's magnetic shield and collide with atoms and molecules in our atmosphere. these collisions result in countless little bursts of light, called photons, which make up the aurora.

auroras are generated by charged solar particles hitting molecules in earth's atmosphere. this usually happens in high latitudes, because our planet’s magnetic field tends to funnel these particles toward the poles. that’s why it can be experienced in northern ohio.