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3 years ago

17. A 120 m long train is moving in a direction with speed 20 m/s. A train B moving with 30

1 answer:

4 0

Answer is D.

Speed:
Use relative speed to simplify the situation. Since the trains are moving in opposite directions, you can add the speeds and pretend the first train is stationary (moving at 0m/s) and the second train is moving at 50m/s.

Distance:
The front of the second train needs to travel 120m to get from the front to the back of the first train. When the front of the second train is at the back of the first train, the back of the second train is still 10m in front of the first train. The back therefore has to travel 130m to clear the first train. The total distance over which the trains are overlapping in this scenario is therefore 120 + 130 = 250m.

You have speed and you have distance so now just calculate time:

v = d / t
50 = 250 / t
t = 5s

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A block weighing 3.7 kg is suspended from the ceiling of a truck trailer by a hanging bungee cord. The cord has a cross-sectiona

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Answer:

$Y = 2.27 \times 10^{10} N/m^2$

Explanation:

Natural length of the string is given as

$L_o = 43 cm$

length of the string while block is hanging on it

$L = 53 cm$

extension in length is given as

$\Delta L = 10 cm$

now we have strain in the string is given as

$strain = \frac{\Delta L}{L}$

$strain = \frac{{10 cm}{43 cm}$

$strain = 0.23$

similarly we will have cross-sectional area of the string is given as

$A = 40 \times 10^{-6} m^2$

now the stress in the string is given as

$Stress = \frac{T}{A}$

$Stress = \frac{mg}{A}$

$Stress = \frac{3.7 \times 9.81}{40 \times 10^{-6}}$

$stress = 9.07 \times 10^5 N/m^2$

Now Young's Modulus is given as

$Y = \frac{stress}{strain}$

$Y = \frac{9.07 \times 10^5}{40\times 10^{-6}}$

$Y = 2.27 \times 10^{10} N/m^2$

5 0

3 years ago

Is the net force on an object moving with uniform velocity zero or not zero?

NikAS [45]

Answer:

Zero

Explanation:

The net force acting on an object moving with uniform velocity is zero. This is an accordance with the Newton's first law of motion.

Newton's first law of motion states that a body will continue in its state of rest or uniform motion unless it is acted upon by an external force.

Since this body is moving with uniform motion, it is not accelerating. When a body is acceleration, the net force on it is not zero.

But this one is moving with uniform motion. The net force on the body is balanced and zero.

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3 years ago

Which of the following best describes the shape of Earth's orbit?

nikklg [1K]

Elliptical, as shown by most projections

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3 years ago

A visitor to a lighthouse wishes to determine the height of the tower. She ties a spool of thread to a small rock to make a simp

Wittaler [7]

Answer:

l = 10.16 m

Explanation:

In this case, we have the period of oscillation of the pendulum is 6.4 s. It is required to find the height of the tower.

We know that the pendulum executes SHM. Let l is the height of the tower. The time period of simple pendulum is given by :

$T=2\pi \sqrt{\dfrac{l}{g}}$

g is acceleration due to gravity

We need to rearrange the above equation such that,

$l=\dfrac{T^2g}{4\pi ^2}\\\\l=\dfrac{(6.4)^2\times 9.8}{4\pi ^2}\\\\l=10.16\ m$

So, the height of the tower is 10.16 m.

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4 years ago

Unlike velocity, speed is scalar, which means it is described by

slava [35]

Answer:

Magnitude

Explanation:

Scalar quantitys have no direction only a size aka magnitude

6 0

3 years ago