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3 years ago

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1. Two firefighters are fighting a fire with identical water hoses and nozzles, except that one is holding the hose straight so

that the water leaves the nozzle in the same direction it comes, while the other holds it backward so that the water makes a U-turn before being discharged. Which firefighter will experience a greater reaction force

1 answer:

ololo11 [35]3 years ago

4 0

Answer:

The firefighter who holds the hose in the backward direction will experience greater force.

Explanation:

Lets take

mass flow rate = m

Inlet velocity = v₁

Exit velocity = v₂

When water leaves in the same direction ,then change in the linear momentum = m (v₂ - v₁)

And we know that change in the linear momentum is known as force.

F₁ =m (v₂ - v₁) ----------1

When water leaves in the opposite direction(U turn) ,then change in the linear momentum = m (v₂ +v₁)

F₂= m (v₂ +v₁) --------2

F₂ >F₁

There fore when water leaves in the U turn pipe will feel more force.

The firefighter who holds the hose in the backward direction will experience greater force.

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Read 2 more answers

A rock is thrown from a height of 2.0 m at a window that is located 9.0 m above the ground. The initial velocity of the rock is

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Answer:

The value is $x = 11.81 \ m$

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The angle at which it is thrown is $\theta = 40$

Generally the vertical component of the velocity of the stone is mathematically represented as

$v_y = 20 sin (40)$

=> $v_y = 12.86 \ m/s$

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$d = h + v_yt + \frac{1}{2} gt^2$

=> $9 = 2 +12.86 t + \frac{1}{2} * - 9.8 t^2$

Here g is negative -9.8 m/s^2 because the direction of the stone is against gravity

So

$4.9 t^2 -12.86 t + 7 =0$

Solving this quadratic equation using quadratic formula we obtain

t = 0.770 s

Generally the velocity of the stone on the x axis is mathematically represented as

$v_x = 20 * cos(40 )$

=> $v_x = 15.32 \ m/s$

Generally the distance between the person throwing the rock and the window is mathematically represented as

$x = v_x * t$

=> $x = 15.32 * 0.771$

=> $x = 11.81 \ m$

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