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Mars2501 [29]
3 years ago
6

A block (mass = 74.0 kg) is hanging from a massless cord that is wrapped around a pulley (moment of inertia = 1/2MR2 kg · m2, wh

ere M = 7.9 is the mass of the pulley and R=1.4 is its radius ), as the drawing shows. Initially the pulley is prevented from rotating and the block is stationary. Then, the pulley is allowed to rotate as the block falls. The cord does not slip relative to the pulley as the block falls. Assume that the radius of the cord around the pulley remains constant at a value of r=R=1.4 m during the block's descent, and the distance of the block at initial position to the floor is 7.0 m. What is the angular velocity in round per minute when the block drops to the floor? Use g = 10 m/s2.
Physics
1 answer:
katen-ka-za [31]3 years ago
4 0

Answer:

51.2m/s

Explanation:

Gravity force acting on the block:

F = mg = 74 * 10 = 740 N

Torque acting on the pulley:

T = FR = 740 * 1.4 = 1036 Nm

Moments of inertia of the solid pulley

I = \frac{1}{2}MR^2 = 0.5*7.9*1.4^2 = 7.742 kgm^2

The angular acceleration of the pulley after release:

\alpha = \frac{T}{I} = \frac{1036}{7.742} = 133.8 rad/s^2

The linear acceleration or the rope

a = \alpha R = 133.8 * 1.4 = 187.34 m/s^2

The time it takes for the block to reach the floor:

s = \frac{1}{2}at^2

t^2 = \frac{2s}{a} = \frac{2 * 7}{187.34} = 0.0747

t = \sqrt{0.0747} = 0.273 s

The final velocity at the floor would be

v = at = 187.34 * 0.273 = 51.2 m/s

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SVEN [57.7K]

Answer:

No, because she is hoping that people will vote for her.

Explanation:

Altruism is when you do something for others and have very little expectation of getting something in return. In this case, Janetta expected something in return from her friends. We may not also be sure of the sincerity of Janetta appreciating friendship. From the above definition of altruism, we conclude that Janetta's actions are not altruistic because she hoped that people will vote for her.

3 0
3 years ago
Solar radiation makes several other energy sources possible, including ________
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Answer:

a

Explanation:

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6 0
2 years ago
Read 2 more answers
Which of the following is an example of a force?
strojnjashka [21]

The answer would be d!

6 0
3 years ago
The component of the external magnetic field along the central axis of a 18 18 turn circular coil of radius 27.0 27.0 cm decreas
madreJ [45]

Answer:

Induced current I = 0.44 A

Explanation:

given data

no of turn N = 18

radius  = 27.0 cm

resistance of the coil = 4.50 Ω

time = 2.90 s

magnetic field  = 1.90 T to 0.500 T

solution

we get Induced EMF that is

E = - dφ ÷ dt    ..............1

E = - N × A × (B2 - B1) ÷ Δt

E = N × A × (B1 - B2) ÷ Δt

area of cross section of the coil A = π × r²

area of cross section = 3.14 × (0.27)²

area of cross section = 0.228 m²

Initial magnetic field B1   = 1.9 T

and  

Final magnetic field B2   = 0.5 T

time      Δt = 3.7 s

put here value and we get

E  =  \frac{18 \times 0.228 \times (1.9-0.5)}{2.90}  

E  = 1.98 V

and  

Induced current I is express as

Induced current I = E  ÷ R    ................2

Induced current I = \frac{1.98}{4.5}

Induced current I = 0.44 A

3 0
2 years ago
A 2.10 X 10^3 kg car starts from rest at the top of a 5.0
xeze [42]

Answer:

3.80 m/s

Explanation:

Solution: From the question we have:

A 2.10 x 10^3 kg car starts from rest at the top of a 5.0 m long driveway that is sloped at 20 degrees with the horizontal.

average friction force of 4.0 x 10^3 N impedes the motion

To find out:  find the speed of the car at the bottom of the driveway.

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PE = mgh = 2100×9.8×1.71 = 35,192 J.

KE = PE-work done by frictional force

KE=PE-4000×5

0.5mV^2 = 35192 - 4000×5

1050V^2 = 15,192

V^2 = 14.47

V = 3.80 m/s.

4 0
3 years ago
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