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andreyandreev [35.5K]
3 years ago
13

A 3.0-kg block moves up a 40o incline with constant speed under the action of a 26-N force acting up and parallel to the incline

. What magnitude force must act up and parallel to the incline for the block to move down the incline at constant velocity?
Physics
1 answer:
CaHeK987 [17]3 years ago
3 0

Answer:

it is very hard question for me sorry i cant solve it

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If a CD player uses a 12-V battery and draws 2.0 amps of current, how much power does it use?
IgorC [24]

Answer:

The power is 24 watt .

Explanation:

Given that,

Voltage V= 12-V

Current I = 2.0 A

Using ohm's law

The current is directly proportional to the voltage.

In form of power,

The power is the product of the Current and voltage.

Formula of the power is defined as,

P = I\times V

P = 2.0\times12

P = 24\ watt

Hence, The power is 24 watt .

4 0
2 years ago
Flywheels are large, massive wheels used to store energy. They can be spun up slowly, then the wheel's energy can be released qu
Kruka [31]

Answer: a) 1766 sec. b) 55.5 MJ c) 13.9 MW d) -12,944 Nm

Explanation:

a) The torque and  the angular acceleration, are related by the following expression, which resembles very much to the Newton's 2nd Law for point masses:

ζ = I . γ, where ζ=external torque, I = rotational inertia and γ = angular acceleration.

We also know that a flywheel is a solid disk, so the rotational inertia for this type of body is equal to MR² / 2.

By definition, angular acceleration is the rate of change of angular velocity with time, so we can write the following:

γ = ωf -ω₀ / t

Assuming that the flywhel starts from rest, we know that ω₀ = 0, and ωf = 12,000 rpm.

As all the units are given in SI units, it is advisable to convert the rpm to rad/sec, as follows:

12,000 rpm = 12,000 rev. (2π/rev) . (1min/60 sec) = 400 π rad/sec

Returning to the original equation, we have:

ζ = MR² / 2 . (ωf/ t)

Replacing by the values, and solving for t, we have:

t = 250 Kg. (0.75)² m² . 400 π / 2. 50 Nm = 1,766 sec.

b) Due to the flywheel is just rotating, all the stored energy is rotational kinetic energy, which can be written as follows:

K = 1/2 I ωf² = 1/2 (MR²/2) ωf² = 1/4. 250 Kg. (0.75)² m². (400π)²

K= 55.5 MJ

c) Power is defined as energy delivered in a given time.

The energy delivered, is just the half of the originally stored value, i.e. , 55.5 MJ /2, equal to 27.75 MJ.

Dividing this value by 2.0 sec, we have the average power delivered to the machine, that we found to be equal to 27.75 MJ / 2s =  13. 9 MW

d) Using the same relationship than in a), we can write the following:

ζ = I. γ

I remains the same (as the flywheel is the same), so the only unknown is the angular acceleration.

Angular acceleration, by definition, is as follows:

γ = ωf - ω₀ / t

We know the value of ω₀, as it is the top speed value that we have already got,i.e., 400 π rad/sec.

We don't know the value for ωf, but we know the value of the rotational kinetic energy after 2.0 secs, which is equal to the half of the one we obtained in step b).

So, we can write the following:

Kf = 1/2 I ωf² = 1/2 (1/2 I ω₀²) ⇒ 1/ 2 ωf² = 1/4 ω₀² ⇒ωf = ω₀/√2

Replacing in the expression for angular acceleration:

γ = (ω₀/√2 - ω₀) / t = -0.29. 400. π/ 2 rad/sec²= -184.1 rad/sec²

Finally, we can get the torque as follows:

ζ = (250 kg. (0.75)² m² /2) . 184.1 rad/sec² = -12,944 Nm

6 0
3 years ago
Which two surfaces have the lowest coefficient of friction
jok3333 [9.3K]

Answer:

Explanation:

As an example, ice on steel has a low coefficient of friction – the two materials slide past each other easily – while rubber on pavement has a high coefficient of friction – the materials do not slide past each other easily. The coefficients of friction ranges from near 0 to greater than 1.

5 0
2 years ago
A race car decelerating by 3 m /s to 10 m / s has an acceleration of 25
Scilla [17]

Answer:

then it will stop

Explanation:

7 0
3 years ago
Is torque only produced when the force is applied perpendicular to the moment arm?
trasher [3.6K]
Yes. Only a perpendicular component produces a torque.
8 0
2 years ago
Read 2 more answers
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