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Nonamiya [84]
3 years ago
6

Một đĩa tròn có bán kính 20cm đang đứng yên, được quanh nhanh dần đều sau 10s thì đạt vận tốc góc 180 vòng/phút. Hãy xác định: a

. Gia tốc góc của đĩa và số vòng đĩa quay được. b. Khi đang quay với 180 vòng/phút thì đĩa bị hãm phanh với lực không đổi sau 10s thì còn 90 vòng/phút. Tính gia tốc góc, số vòng và thời gian đĩa quay được kể từ lúc hãm phanh.
Physics
1 answer:
masya89 [10]3 years ago
7 0

this made my day happyf77d3

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a body of radius R and mass m is rolling horizontally without slipping with speed v. it then rolls us a hill to a maximum height
ki77a [65]

Answer:

mR²/2

Explanation:

Here is the complete question

An object of radius′

R′  and mass ′

M′  is rolling horizontally without slipping with speed ′

V′

. It then rolls up the hill to a maximum height h = 3v²/4g. The moment of inertia of the object is (g= acceleration due to gravity)

Solution

Since it rolls without slipping, there is no friction. So, its initial mechanical energy at the horizontal surface equals its final mechanical energy at the top of the hill.

Since the object is rolling initially, and on horizontal ground, it initial energy is kinetic and made up of rotational and translational kinetic energy.

So, E = K + K'

E = 1/2mv² + 1/2Iω² where m = mass of object, v = speed of object, I = moment of inertia of object and ω = angular speed of object = v/r where v = speed of object and R = radius of object.

Also, the final mechanical energy of the object, E' is its potential energy at the top of the hill. So, E' = mgh.

Since E = E',

1/2mv² + 1/2Iω² = mgh

substituting the values of ω and h into the equation, we have

1/2mv² + 1/2Iω² = mgh

1/2mv² + 1/2I(v/R)²= mg(3v²/4g)

Expanding the brackets, we have

1/2mv² + 1/2Iv²/R²= 3mv²/4

Dividing through by v², we have

1/2m + I/2R²= 3m/4

Subtracting m/2 from both sides, we have

I/2R² = 3m/4 - m/2

Simplifying, we have

I/2R² = m/4

Multiplying through by 2R², we have

I = m/4 × 2R²

I = mR²/2

6 0
3 years ago
Juan rides his horse with a constant<br> speed of 18 km/h. How far can he travel<br> in 1/2 hour?
Brut [27]

Answer:

He traveled 9km

Explanation:

To do this problem you need to use the equation which is Speed= distance/time and this problem gives you the speed which is 18 km/h and it gives you the time 1/2 hour so you write the equation 18= d/ 1/2 which his distance is 9km

3 0
3 years ago
The amount of dissolved oxygen in water may decrease because of the 
Elanso [62]
<span>The amount of dissolved oxygen in water may decrease because of the increase in organic matter in the water. <span>Aquatic organisms breathe and use oxygen. Large amounts of oxygen are consumed by the decomposition of bacteria (when there are large amounts of dead matter to decompose, there will be a significant number of bacteria). Examples: dead organic matter (algae), wastewater, garden waste, oils and fats, all this results in a decrease in dissolved oxygen in the water.</span></span>
8 0
3 years ago
Read 2 more answers
I would love to stretch a wire from our house to the Shop so I can 'call' my husband in for meals. The wire could be tightened t
dezoksy [38]
Note: I'm not sure what do you mean by "weight 0.05 kg/L". I assume it means the mass per unit of length, so it should be "0.05 kg/m".

Solution:
The fundamental frequency in a standing wave is given by
f= \frac{1}{2L} \sqrt{ \frac{T}{m/L} }
where L is the length of the string, T the tension and m its mass. If  we plug the data of the problem into the equation, we find
f= \frac{1}{2 \cdot 24 m} \sqrt{ \frac{240 N}{0.05 kg/m} }=1.44 Hz

The wavelength of the standing wave is instead twice the length of the string:
\lambda=2 L= 2 \cdot 24 m=48 m

So the speed of the wave is
v=\lambda f = (48 m)(1.44 Hz)=69.1 m/s

And the time the pulse takes to reach the shop is the distance covered divided by the speed:
t= \frac{L}{v}= \frac{24 m}{69.1 m/s}=0.35 s
7 0
3 years ago
The Shinkansen (bullet train in Japan) makes a trip from Tokyo Station to Kyoto station in 2 hours and 14 min. The distance trav
11Alexandr11 [23.1K]

Answer:

v =  57.2 m/s

Explanation:

The average velocity of the train can be defined as the total distance covered by the train divided by the time taken by the train to cover that distance. Therefore, we will use the following formula to find the average velocity of the train:

v = s/t

where,

s = distance covered = 460 km = (460 km)(1000 m/1 km) = 4.6 x 10⁵ m

t = time taken to cover the distance = 2 h 14 min

Now, we convert it into minutes:

t = (2 h)(60 min/1 h) + 14 min

t = 120 min + 14 min = (134 min)(60 s/1 min)

t = 8040 s

Therefore, the value of velocity will be:

v = (4.6 x 10⁵ m)/8040 s

<u>v =  57.2 m/s</u>

7 0
3 years ago
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