| This guy
doesn't know when to quit. Since he causes friction wherever he speaks
and his words carry little weight, it's not unusual for his audience to
find unique ways to cut his speeches short.
Speaking of friction and weight, our orator weighs 800 N and is standing firmly on the 100-N crate as it is being pulled away. If the truck is accelerating (backwards) at 4 m/s2, what is the minimum coefficient of static friction between the crate and the orator's shoes? |
The weight of the crate does not
matter. The mass of the person is (800 N) / 10 m/s2 = 80 kg,
so the force causing acceleration (acting parallel to the surface) is (80
kg)(4 m/s2) = 320 N. The friction force must be balancing this.
The minimum coefficient is therefore
(320 N) / (800 N) = 0.4 (a lower coefficient would mean a lower friction force and result in a non-zero net force) |