# physics

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A car tire rotates with an average angular speed of 29rad/s.
In what time interval will the tire rotate 3.5 times?

• physics -

The speed of a moving bullet can be deter-
mined by allowing the bullet to pass through
two rotating paper disks mounted a distance
72 cm apart on the same axle. From the
angular displacement 32.1  of the two bul-
let holes in the disks and the rotational speed
862 rev/min of the disks, we can determine
the speed of the bullet.

What is the speed of the bullet?

• physics -

The tub of a washer goes into its spin-
dry cycle, starting from rest and reaching an
angular speed of 4.2 rev/s in 4.5 s . At this
point the person doing the laundry opens the
lid, and a safety switch turns off the washer.
The tub slows to rest in 12.9 s .
Through how many revolutions does the
tub turn? Assume constant angular accelera-
tion while it is starting and stopping.

• physics -

In the Bohr model of the hydrogen atom,
the speed of the electron is approximately
1.97 × 106 m/s.
Find the central force acting on the electron
as it revolves in a circular orbit of radius
4.72 × 10−11 m.

• physics -

39.92