Astronomers currently estimate the age of the universe to be:.

1 answer:

7 0

Nearly 14 billion years, according to astronomers. Happy to help!

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soldier1979 [14.2K]

Answer:

W = 7000 J

Explanation:

To solve this problem we use that the speed of the bicycle is constant, therefore its acceleration is zero

F -fr = 0

F = fr

where F is the force applied by the child

Work is defined by

W = F. x

W = F x cos θ

in this case the child's force is parallel to the movement, therefore the angle is zero and cos 0 = 1

let's calculate

W = 35 200

W = 7000 J

8 0

3 years ago

Gemiola [76]

Answer:

α = 200*π rad/sec²

Explanation:

If the disk drive revolves once every 0.05 sec, this means that the angular velocity can be expressed as follows:

$\omega = \frac{2*\pi}{0.05s} = 40*\pi rad/sec$

(just applying the definition of angular velocity)
Now, it the disk started from rest, and took two revolutions to reach to full speed, assuming that the angular acceleration is constant, we can find the angular acceleration applying this kinematic equation:

$\omega_{f} ^{2} -\omega_{0} ^{2} = 2*\alpha * \Delta\theta$

where Δθ, is the angle rotated while it went from rest to full speed, i.e., 2 revolutions, or 2*π rads.
Replacing by the value that we found for ωf (as ω₀ = 0), we can solve for α :

$\alpha =\frac{\omega_{f}^{2} }{2*\Delta\theta} = \frac{(40*\pi)^{2} }{2*2*2*\pi } =\\ \\ \alpha = 200*\pi rad/sec2$