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ella [17]
3 years ago
8

A uniform-density 7 kg disk of radius 0.21 m is mounted on a nearly frictionless axle. Initially it is not spinning. A string is

wrapped tightly around the disk, and you pull on the string with a constant force of 44 N through a distance of 0.9 m. Now what is the angular speed?
Physics
2 answers:
Thepotemich [5.8K]3 years ago
6 0

Answer:

22.65 rad/s

Explanation:

m = 7 kg, r = 0.21 m, F = 44 N, d = 0.9 m

Moment of inertia, I = 1/2 mr^2 = 0.5 x 7 x 0.21 x 0.21 = 0.15435 kg m^2

Work done, W = F x d = 44 x 0.9 = 39.6 J

according to the work energy theorem

Change in the kinetic energy of rotation = Work done

1/ 2 x I x ω^2 = W

0.5 x 0.15435 x ω^2 = 39.6

ω^2 = 513.12

ω = 22.65 rad/s

GREYUIT [131]3 years ago
5 0

Answer:

\omega = 22.67 rad/s

Explanation:

Here we can use energy conservation

As per energy conservation conditions we know that work done by external source is converted into kinetic energy of the disc

Now we have

W = \frac{1}{2}I\omega^2

now we know that work done is product of force and displacement

so here we have

W = F.d

W = (44 N)(0.9 m) = 39.6 J

now for moment of inertia of the disc we will have

I = \frac{1}{2}mR^2

I = \frac{1}{2}(7 kg)(0.21^2)

I = 0.154 kg m^2

now from above equation we will have

39.6 = \frac{1}{2}(0.154)\omega^2

\omega = 22.67 rad/s

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b) Since the two protons repel each other and force of repulsion reduces as the dI stance between the protons increases, the maximum acceleration occurs at the minimum distance apart for the two protons.

Force of repulsion acting on each proton is given through Coulomb's law as

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ma = (kq₁q₂/r²)

a = (kq₁q₂/r²m)

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a = [(8.988 × 10⁹) × (1.602 × 10⁻¹⁹)²] ÷ [(7.2 × 10⁻¹⁰)² × (1.673 × 10⁻²⁷)]

a = (2.660 × 10¹⁷) m/s²

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