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3 years ago

The 480 g bar is rotating as shown what is the angular momentum of the bar about the axle?

1 answer:

4 0

On a similar problem wherein instead of 480 g, a 650 gram of bar is used:

Angular momentum L = Iω, where
I = the moment of inertia about the axis of rotation, which for a long thin uniform rod rotating about its center as depicted in the diagram would be 1/12mℓ², where m is the mass of the rod and ℓ is its length. The mass of this particular rod is not given but the length of 2 meters is. The moment of inertia is therefore 
I = 1/12m*2² = 1/3m kg*m² 

The angular momentum ω = 2πf, where f is the frequency of rotation. If the angular momentum is to be in SI units, this frequency must be in revolutions per second. 120 rpm is 2 rev/s, so 
ω = 2π * 2 rev/s = 4π s^(-1) 

The angular momentum would therefore be 
L = Iω 
= 1/3m * 4π 
= 4/3πm kg*m²/s, where m is the rod's mass in kg. 

The direction of the angular momentum vector - pseudovector, actually - would be straight out of the diagram toward the viewer. 

Edit: 650 g = 0.650 kg, so 
L = 4/3π(0.650) kg*m²/s 
≈ 2.72 kg*m²/s

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How do you find acceleration due to gravity with time and height given?

Feliz [49]

Here, height is given which will be the distance for a freely falling object.

The velocity will be

$v=\text{ }\frac{h}{t}$

and the acceleration will be

$a=\frac{v}{t}$

In this way, the formula works.

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1 year ago

1. A mass is on a level plane, it has a weight of 20N. What is the coefficient of kinetic friction if an applied force

Arturiano [62]

Answer:

0.4

Explanation:

F-Fr=ma where F is applied force, Fr is friction, m is mass and a is acceleration.

Since the mass is moving with a constant velocity, there's no acceleration hence

$F=Fr=\mu N$ where N is the weight of object and \mu is coefficient of kinetic friction.

$F=\mu N and making [tex]\mu$ the subject

$\mu=\frac {F}{N}$

Substituting F for 8 N and N for 20 N

$\mu=\frac {8}{20}=0.4$

Therefore, coefficient of kinetic friction is 0.4

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4 years ago

A 2500-ohm is connected to a 110v power supply. What is the current through the resistor

Assoli18 [71]

Answer:

0.044 amps

Explanation:

Givens

R = 2500 ohms

E = 110 volts

I = ?

Equation

I = E/R

Solution

I = 110/2500

I = 0.044 amps

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3 years ago

A ball is tossed with enough speed straight up so that it is in the air several seconds. (a) What is the velocity of the ball wh

irina1246 [14]

(a) Zero

When the ball reaches its highest point, the direction of motion of the ball reverses (from upward to downward). This means that the velocity is changing sign: this also means that at that moment, the velocity must be zero.

This can be also understood in terms of conservation of energy: when the ball is tossed up, initially it has kinetic energy

$K=\frac{1}{2}mv^2$

where m is the ball's mass and v is the initial speed. As it goes up, this kinetic energy is converted into potential energy, and when the ball reaches the highest point, all the kinetic energy has been converted into potential energy:

$U=mgh$

where g is the gravitational acceleration and h is the height of the ball at highest point. At that point, therefore, the potential energy is maximum, while the kinetic energy is zero, and so the velocity is also zero.

(b) 9.8 m/s upward

We can find the velocity of the ball 1 s before reaching its highest point by using the equation:

$a=\frac{v-u}{t}$

where

a = g = -9.8 m/s^2 is the acceleration due to gravity, which is negative since it points downward

v = 0 is the final velocity (at the highest point)

u is the initial velocity

t = 1 s is the time interval

Solving for u, we find

$u=v-at = 0 -(-9.8 m/s^2)(1 s)= +9.8 m/s$

and the positive sign means it points upward.

(c) -9.8 m/s

The change in velocity during the 1-s interval is given by

$\Delta v = v -u$

where

v = 0 is the final velocity (at the highest point)

u = 9.8 m/s is the initial velocity

Substituting, we find

$\Delta v = 0 - (+9.8 m/s)=-9.8 m/s$

(d) 9.8 m/s downward

We can find the velocity of the ball 1 s after reaching its highest point by using again the equation:

$a=\frac{v-u}{t}$

where this time we have

a = g = -9.8 m/s^2 is the acceleration due to gravity, still negative

v is the final velocity (1 s after reaching the highest point)

u = 0 is the initial velocity (at the highest point)

t = 1 s is the time interval

Solving for v, we find

$v = u+at = 0 +(-9.8 m/s^2)(1 s)= -9.8 m/s$

and the negative sign means it points downward.

(e) -9.8 m/s

The change in velocity during the 1-s interval is given by

$\Delta v = v -u$

where here we have

v = -9.8 m/s is the final velocity (1 s after reaching the highest point)

u = 0 is the initial velocity (at the highest point)

Substituting, we find

$\Delta v = -9.8 m/s - 0=-9.8 m/s$

(f) -19.6 m/s

The change in velocity during the overall 2-s interval is given by

$\Delta v = v -u$

where in this case we have:

v = -9.8 m/s is the final velocity (1 s after reaching the highest point)

u = +9.8 m/s is the initial velocity (1 s before reaching the highest point)

Substituting, we find

$\Delta v = -9.8 m/s - (+9.8 m/s)=-19.6 m/s$

(g) -9.8 m/s^2

There is always one force acting on the ball during the motion: the force of gravity, which is given by

$F=mg$

where

m is the mass of the ball

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

According to Newton's second law, the resultant of the forces acting on the body is equal to the product of mass and acceleration (a), so

$mg = ma$

which means that the acceleration is

$a= g = -9.8 m/s^2$

and the negative sign means it points downward.

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3 years ago

Density is given in ____. a. Pa/cm3 c. g/s2 b. N/m2 d. g/cm3

Ainat [17]

Density is defined as [mass] / [volume] .

The only choice listed with those physical dimensions is 'd' .

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4 years ago