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Allisa [31]
3 years ago
14

Why are bridges declared unsafe after a long use​

Physics
1 answer:
lina2011 [118]3 years ago
8 0

After it's long use, the bridge continuously undergoes through alternating strains. in result, the elastic strength of the bridge gets reduced. while the process goes on the bridge makes elastic fatigue and a permanent change happens which makes it collapse which is the reason why bridges are declared unsafe after a long use​ :)

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A 2137 kg car moving east at 12.91 m/s collides with a 3264 kg car moving north. The cars stick together and move as a unit afte
IRINA_888 [86]

Answer:

The speed of the 3264 kg car before collision is 6.32 m/s

Explanation:

Let first car, mass m₁, moving east be moving with velocity, v₁ and second car, mass m₂, moving north be moving with velocity, v₂. Let the velocity of the two cars after collision be v₃

In a Collison (whether elastic or inelastic), momentum is always conserved.

Momentum before collision = momentum after collision.

Momentum before collision = m₁v₁ + m₂v₂

v₁ = (12.91î) m/s in vector form, m₁ = 2137 kg

v₂ = ?, v₂ = (v₂j) m/s in vector form, m₂ = 3264 kg

Momentum before collision = (2137)(12.91î) + (3264)(v₂j) = (27590î + 3264v₂j) kgm/s

Momentum after collision = (total mass of the cars after collision) × (velocity of the stuck-together cars after collision)

Total mass of the cars after collision = m₁ + m₂ = 2137 + 3264 = 5401 kg

Velocity after collision, v₃ = 6.38 m/s In the N36.8°E direction, put in vector form,

v₃ = (6.38 cos 36.8°î + 6.38 sin 36.8°j)

v₃ = (5.11î + 3.82j) m/s

Momentum after collision = 5401 (5.11î + 3.82j) = (27590î + 20641.4j) kgm/s

Momentum before collision = momentum after collision.

(27590î + 3264v₂j) = (27590î + 20641.4j)

Comparing components

3264v₂ = 20641.4j

v₂ = 6.32 m/s

Hope this Helps!!!

6 0
3 years ago
The Bay of Fundy has the greatest tidal ranges on Earth. What can you infer about the Bay of Fundy?
swat32

C is the answer

The Bay of Fundy has the greatest tidal ranges on Earth. What can you infer about the Bay of Fundy?

a.

It faces the moon more often than other places on Earth.

b.

It has many rocky beaches.

c.

It is a long, narrow inlet.

d.

Its tides cannot be predicted accurately.

4 0
3 years ago
Explain how the thermal energy of an isolated system changes with time if the mechanical energy of that system is constant.​
Naddika [18.5K]

Answer:

Thermal energy of an isolated system changes with time If the mechanical energy of that system is constant according to the first law of thermodynamics, which states that thermal energy of an isolated system can still change as long as the total energy of that system does not change.

Explanation:

6 0
3 years ago
"Fifteen hundred years ago everybody knew the Earth was the center of the universe. Five hundred years ago, everybody knew the E
Elenna [48]
I believe its B, constantly changing
7 0
3 years ago
Read 2 more answers
To a good approximate, the only external force that does work on a cyclist moving on level ground is the force of air resistance
mart [117]

Answer:

a. 120 W

b. 28.8 N

Explanation:

To a good approximate, the only external force that does work on a cyclist moving on level ground is the force of air resistance. Suppose a cyclist is traveling at 15 km/h on level ground. Assume he is using 480 W of metabolic power.

a. Estimate the amount of power he uses for forward motion.

b. How much force must he exert to overcome the force of air resistance?

(a) He is 25% efficient, therefore the cyclist will be expending 25% of his power to drive the bicycle forward

Power = efficiency X metabolic power

= 0.25 X 480

= 120 W

(b)

power if force times the velocity

P = Fv

convert  15 km/h to m/s

v = 15 kmph = 4.166 m/s

F = P/v

= 120/4.166

= 28.8 N

definition of terms

power is the rate at which work is done

force is that which changes a body's state of rest or uniform motion in a straight line

velocity is the change in displacement per unit time.

3 0
3 years ago
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