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earnstyle [38]
3 years ago
14

A skateboarder rolls off a 2.5 m high bridge into the river. If the skateboarder was originally moving at 7.0 m/s, how much time

did the skateboarder spend in the air and how far will be his final position from the bridge?
Physics
1 answer:
saul85 [17]3 years ago
3 0

Answer:

  t = 0.714 s and  x = 5.0 m

Explanation:

This is a projectile throwing exercise, in this case when the skater leaves the bridge he goes with horizontal speed

         vₓ = 7.0 m / s

Let's find the time it takes to get to the river

         y = y₀ + v_{oy} t - ½ g t²

the initial vertical speed is zero and when it reaches the river its height is zero

        0 = y₀ + 0 - ½ g t²

        t = \sqrt{\frac{2y_o}{g}  }

        t = ra 2 2.5 / 9.8

        t = 0.714 s

the distance traveled is

       x = vₓ t

       x = 7.0 0.714

       x = 5.0 m

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P5. A bullet with an initial velocity of 280 m/s in the x-direction penetrates an initially stationary block of mass 11 kg and e
aliya0001 [1]

Answer:

the mass of the bullet is 10.5 g

Explanation:

Given;

initial velocity, u₁ = 280 m/s

final velocity of the bullet, v₁ = 70 m/s

final velocity of the block, v₂ = 0.2 m/s

mass of the block, m₂ = 11 kg

initial velocity of the block, u₂ = 0

let the mass of the bullet = m₁

Apply the principle of conservation of linear momentum for elastic collision to calculate the mass of the bullet.

m₁u₁ + m₂u₂ = m₁v₁  + m₂v₂

280m₁  +  11(0)  = 70m₁  +  11 x 0.2

280m₁ = 70m₁  + 2.2

280m₁ - 70m₁  = 2.2

210m₁ = 2.2

m₁ = 2.2/210

m₁ = 0.0105 kg

m₁ = 10.5 g

Therefore, the mass of the bullet is 10.5 g

7 0
3 years ago
A police car is at rest parallel to the highway and measures the speed of cars. It sends the signal with a frequency of 1200 Hz,
masha68 [24]

Answer:

a) The car was moving at a speed of 29.167\ m.s^{-1}

b) The negative sign of v_o denotes that the observer is coming towards the police car which is the source of the sound.

c) f_o=1283.33\ Hz

Explanation:

Given:

  • original frequency of the source, f=1200\ Hz
  • speed of the source, v_s=0\ m.s^{-1}
  • velocity of the obstacle car be, v_o
  • speed of sound, s=350\ m.s^{-1}
  • observed frequency, f_o=1100\ Hz

<u>Using the equation from the Doppler's effect:</u>

\frac{f_o}{f} =\frac{(s+v_o)}{(s-v_s)}

\frac{1100}{1200} =\frac{(350+v_o)}{350-0}

v_o=-29.167\ m.s^{-1}

a)

The car was moving at a speed of 29.167\ m.s^{-1}

b)

The negative sign of v_o denotes that the observer is coming towards the police car which is the source of the sound.

c)

Now when, v_s=50\ m.s^{-1}

Then, f_o=?

Using the Doppler's eq.:

\frac{f_o}{1200} =\frac{(350+(-29.167))}{(350-50)}

f_o=1283.33\ Hz

3 0
3 years ago
What is the momentum of a 0.000015 kg mosquito flying straight at you with a velocity of 5.20 m/s?
Setler [38]

Answer:

Momentum, p=7.8\times 10^{-5}\ N-m

Explanation:

Given that,

Mass of a mosquito, m = 0.000015 kg

Velocity of the mosquito, v = 5.2 m/s

We need to find the momentum of the mosquito. The momentum of an object is given by :

p = mv

Put all the values in the above formula.

p=0.000015\ kg\times 5.2\ m/s\\\\p=0.000078\ N-m\\\\\text{or}\\\\p=7.8\times 10^{-5}\ N-m

So, the momentum of the mosquito is 7.8\times 10^{-5}\ N-m.

3 0
3 years ago
What information do you think the temperatures of stars give us?
Paul [167]

Explanation:

One way of classifying stars is by their temperature .

or

Science strives to be able to describe how stars and planets form and evolve. This requires theories to describe the processes which include:

Star and planet formation

Star and planet composition

Stellar and solar system evolution

The nuclear processes happening inside stars

The scientific method means that all theories are put to the test. By measuring or calculating the temperature, age and composition of other planets and stars the theories can be tested. If observed values of these parameters are not predicted by theories, then the theories are wrong and need to be revised or replaced.

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3 years ago
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What is the best description of a mechanical wave?
gizmo_the_mogwai [7]

Answer:

A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium. While waves can move over long distances, the movement of the medium of transmission—the material—is limited. Therefore, the oscillating material does not move far from its initial equilibrium position.

Explanation:

8 0
3 years ago
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