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4 years ago

How much work is needed to lift a barbell that has a weight of 445 N a total of 2 meters off ground

Physics

1 answer:

AleksAgata [21]4 years ago

5 0

Answer:

Total work done to lift barbell = 890 J

Explanation:

Given:

Weight of barbell (F) = 445 N

Height (Distance) = 2 meter

Find:

Total work done to lift barbell = ?

Computation:

⇒ Work = Force(F) × Distance

⇒ Total work done to lift barbell = Weight of barbell × Distance

⇒ Total work done to lift barbell = 445 N × 2 meter

⇒ Total work done to lift barbell = 890 J

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A billiard ball with a mass of 0.15 kg has a velocity of 5 m/s. It strikes the bumper of the table perpendicularly and bounces s

Marianna [84]

Initial momentum = 0.15 kg * (-5 m/s) = - 0.75 N*s

final momentum = 0.15 * ( 3 m/s) = 0.45 N*s

Change in momentum = final momentum - initial momentun =

= 0.45N*s - (- 0.75N*s) = 1.2 N*s

Answer: 1.2 N*s

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3 years ago

A computer hard disk starts from rest, then speeds up with an angular acceleration of 190 rad/s2rad/s2 until it reaches its fina

Otrada [13]

Answer:

962 rpm.

Explanation:

given,

angular acceleration = 190 rad/s²

initial angular speed = 0 rad/s

final angular speed = 7200 rpm

= $7200\times\dfrac{2\pi}{60}$

= $754\ rad/s$

we need to calculate the revolution of disk after 10 s.

time taken to reach the final angular velocity

using equation of angular motion

$\omega_f - \omega_i = \alpha t$

$754 - 0 =190\times t$

t = 4 s

rotation of wheel in 4 s

$\theta =\omega_i t+ \dfrac{1}{2}\alpha t$

$\theta = \dfrac{1}{2}\alpha t^2$

$\theta = \dfrac{1}{2}\times 190 \times 4^2$

θ = 1520 rad

$\theta = \dfrac{1520}{2\pi}$

$\theta =242\ rev$

now, revolution of the disk in next 6 s

angular velocity is constant

$\omega_f = \dfrac{\theta_f-\theta_i}{t_f-t_i}$

$754 = \dfrac{\theta_f-1520}{10-4}$

θ_f = 6044 rad

θ_f = $\dfrac{6044}{2\pi}$

revolution of the computer hard disk

θ_f = 962 rpm.

total revolution of the computer disk after 10 s is equal to 962 rpm.

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3 years ago

Is it possible to have motion in the absence of a net force?

Vsevolod [243]

Answer:

It is impossible...

Explanation:

Under no circumstances this is possible because of the Newton’s 1st law of motion that states that a body shall continue its motion forever except the net fore is zero. When two opposing forces contract each other, they cancel out the action of each other and ultimately the net force become zero. If one body has a slightly more or less force then the net force will not be zero and the net magnitude of force will have a direction of motion.

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4 years ago

A student pulls on a rope attached to a box of books and moves the box down the hall. The student pulls with a force of 185N at

Vitek1552 [10]

Answer:

$2.75 m/s^2$

Explanation:

We can solve the problem by writing the equations of motion along the horizontal and vertical direction.

Along the horizontal direction we have:

$T cos \theta - \mu N = ma$ (1)

where

$T cos \theta$ is the horizontal component of the tension, where

T = 185 N is the tension in the rope

$\theta=25^{\circ}$ is the angle between the rope and the horizontal

$\mu N$ is the force of friction, where

$\mu=0.27$ is the coefficient of friction

N is the normal reaction of the floor on the box

m = 35.0 kg is the mass of the box

a is the acceleration

Along the vertical direction we have:

$N+T sin \theta-mg=0$ (2)

where

N is the normal force (upward direction)

$T sin \theta$ is the vertical component of the tension in the rope (upward direction)

$mg$ is the weight of the box (downward direction), where

m = 35.0 kg is the mass of the box

$g=9.8 m/s^2$ is the acceleration due to gravity

From eq.(2) we get:

$N=mg-T sin \theta$

And substituting into (1), we can find the acceleration:

$T cos \theta - \mu (mg-T sin \theta) = ma\\Tcos \theta -\mu mg + \mu T sin \theta = ma\\a=\frac{T cos \theta- \mu mg + \mu T sin \theta}{m}=\\=\frac{(185)(cos 25^{\circ})-(0.27)(35.0)(9.8)+(0.27)(185)(sin 25^{\circ})}{35.0}=2.75 m/s^2$

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3 years ago

What energy comes from electric charge, which is one of the fundamental properties of all matter

4vir4ik [10]

Answer:

A physical property of matter is electric charge. It is caused by an imbalance in the number of protons and electrons in a material. Whether there are more protons than electrons in a substance, it is positively charged if there are more electrons than protons, it is negatively charged.

Explanation:

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3 years ago

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