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eimsori [14]
3 years ago
14

A train of mass 50000 kg starts from rest and moves with uniform acceleration 5 km/h2 then, find its kinetic energy after 30 min

utes.
Physics
1 answer:
r-ruslan [8.4K]3 years ago
7 0

Answer:

12 kJ

Explanation:

Given:

v₀ = 0 km/h

a = 5 km/h²

t = 30 min = 0.5 h

Find: v

v = at + v₀

v = (5 km/h²) (0.5 h) + 0 km/h

v = 2.5 km/h

v = 2.5 km/h × (1000 m/km) × (1 h / 3600 s)

v = 0.694 m/s

KE = ½ mv²

KE = ½ (50,000 kg) (0.694 m/s)²

KE = 12,000 J

KE = 12 kJ

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I stretch a rubber band and "plunk" it to make it vibrate in its fundamental frequency. I then stretch it to twice its length an
Nikitich [7]

Answer:

The new frequency (F₂ ) will be related to the old frequency by a factor of one (1)

Explanation:

Fundamental frequency = wave velocity/2L

where;

L is the length of the stretched rubber

Wave velocity = \sqrt{\frac{T}{\frac{M}{L}}}

Frequency (F₁) = \frac{\sqrt{\frac{T}{\frac{M}{L}}}}{2*L}

To obtain the new frequency with respect to the old frequency, we consider the conditions stated in the question.

Given:

L₂ =2L₁ = 2L

T₂ = 2T₁ = 2T

(M/L)₂ = 0.5(M/L)₁ = 0.5(M/L)

F₂ = \frac{\sqrt{\frac{2T}{0.5(\frac{M}{L})}}}{4*L} = \frac{\sqrt{4(\frac{T}{\frac{M}{L}}})}{4*L} = \frac{2}{2} [\frac{\sqrt{\frac{T}{\frac{M}{L}}}}{2*L}] = F_1

Therefore, the new frequency (F₂ ) will be related to the old frequency by a factor of one (1).

7 0
3 years ago
An object takes 5 seconds to move 2 meters upward. How fast did it go?
jonny [76]

Answer:

2.5

Explanation:

5/2=2.5

8 0
3 years ago
Suppose a 2.0kg bird is flying at a speed of of 1m/s. It’s kinetic energy would be what?
Ganezh [65]

As we know that the formula of kinetic energy will be

KE = \frac{1}{2} mv^2

now here we know that

m = 2 kg

v = 1 m/s

so from the above equation we have

KE = \frac{1}{2}(2)(1^2)

KE = 1 J

7 0
3 years ago
The world speed record on water was set on October
Luda [366]

Answer: Remember speed is distance divided by time, so if he travels 1000 m in 7.045 s, his speed is

(1000 m)/(7.045 s) = 141.9 m/s.

Note there are 1609 metres in a mile, or 1 mi = 1609 m, so m = 1/1609 mi, or

141.9/1609 mi/s = 0.08822 mi/s. Now, note that 1 h = 3600 s, so the speed is

0.08822*3600 mi/h = 317.6 mi/h.

8 0
3 years ago
You are hungry and decide to go to your favorite neighborhood fast-food restaurant. You leave your apartment and take the elevat
Viktor [21]

Answer:

A)  R = (200 i ^ + 100 j ^ + 30k ^) m , B)    L = 223.61 m , C)   R = 225.61 m

Explanation:

Part A

This is a vector summing exercise, let's take a Reference System where the z axis corresponds to the height (flights), the x axis is the East - West and the y axis corresponds to the North - South.

Let's write the displacements

Descending from the apartment

10 flights of 3 m each, the total descent is 30 m

                Z = 30 k ^ m

Offset at street level

            L1 = 0.2 i ^ km

            L2 = 0.1 j ^ km

Let's reduce everything to the SI system

          L1 = 0.2 * 1000 = 200 i ^ m

          L2 = 100 j ^ m

The distance traveled is

          R = (200 i ^ + 100 j ^ + 30k ^) m

Part B

The horizontal distance traveled can be found with the Pythagorean theorem for the coordinates in the plane

                L² = x² + y²

                L = √ (200² + 100²)

                L = 223.61 m

Part C

The magnitude of travel, let's use the Pythagorean theorem for the sum

             R² = x² + y² + z²

              R = √ (30² + 200² + 100²)

             R = 225.61 m

7 0
3 years ago
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