PHYSICS COLLEGE

A rescue helicopter is hovering over a person whose boat has sunk. One of the rescuers throws a life preserver straight down to the victim with an initial velocity of 1.50 m/s and observes that it takes 1.2 s to reach the water. How high above the water was the preserver released? Note that the downdraft of the helicopter reduces the effects of air resistance on the falling life preserver, so that an acceleration equal to that of gravity is reasonable. Round your answer to the nearest whole number.

Answers

Answer 1

Answer:

Answer:

The answer is 9 m.

Explanation:

Using the kinematic equation for an object in free fall:

$y = y_o - v_o-(1)/(2)gt^(2)$

In this case:

$v_o = \textrm{Initial velocity} = 1.5[m/s]\nt = \textrm{air time} = 1.2 [s]$ $y_o = 0$

$g = \textrm{gravity} = 9.8 [m/s^(2) ]$

Plugging those values into the previous equation:

$y = 0 - 1.5*1.2-(1)/(2)*9.8*1.2^(2) \ny = -8.85 [m] \approx -9 [m]$

The negative sign is because the reference taken. If I see everything from the rescuer point of view.

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The electrons in the beam of a television tube have a kinetic energy of 2.20 10-15 j. initially, the electrons move horizontally from west to east. the vertical component of the earth's magnetic field points down, toward the surface of the earth, and has a magnitude of 3.00 10-5 t. (a) in what direction are the electrons deflected by this field component? due north due south due east due west (b) what is the magnitude of the acceleration of an electron in part (a)? m/s2

Answers

(a) The electrons move horizontally from west to east, while the magnetic field is directed downward, toward the surface. We can determine the direction of the force on the electron by using the right-hand rule:
- index finger: velocity --> due east
- middle finger: magnetic field --> downward
- thumb: force --> due north
However, we have to take into account that the electron has negative charge, therefore we have to take the opposite direction: so, the magnetic force is directed southwards, and the electrons are deflected due south.

b) From the kinetic energy of the electrons, we can find their velocity by using
$K= (1)/(2)mv^2$
where K is the kinetic energy, m the electron mass and v their velocity. Re-arranging the formula, we find
$v= \sqrt{ (2K)/(m) }= \sqrt{ (2 \cdot 2.20 \cdot 10^(-15) J)/(9.1 \cdot 10^(-31) kg) }=6.95 \cdot 10^7 m/s$

The Lorentz force due to the magnetic field provides the centripetal force that deflects the electrons:
$qvB = m (v^2)/(r)$
where
q is the electron charge
v is the speed
B is the magnetic field strength
m is the electron mass
r is the radius of the trajectory
By re-arranging the equation, we find the radius r:
$r= (mv)/(qB)= ((9.1 \cdot 10^(-31) kg)(6.95 \cdot 10^7 m/s))/((1.6 \cdot 10^(-19) C)(3.00 \cdot 10^(-5) T))=13.18 m$

And finally we can calculate the centripetal acceleration, given by:
$a_c = (v^2)/(r)= ((6.95 \cdot 10^7 m/s)^2)/(13.18 m)=3.66 \cdot 10^(14) m/s^2$

Is the magnet in a compass a permanent magnet or an electromagnet?

Answers

the needle of a compass is a permanent magnet and the north indicator of the compass is a magnetic north pole. the north pole of a magnet lines up with the magnetic field so a suspended compass needle will rotate it lines up with the magnetic field. Answer permanent magnet

The speed of light in a transparent plastic is 2.5x108 m/s. If a ray of light in air(with n-1) strikes this plastic at an angle of incidence of 31.3 degrees, find the angle of the transmitted ray. Select one: a. 31.30 degrees b. 26.08 degrees c, 37.56 degrees d. 38.57 degrees e. 0.67 degrees

Answers

Answer:

Angle of transmitted ray is $29.14^(o)$

Explanation:

According to snell's law we have

$n_(1)sin(\theta _(i))=n_(2)sin(\theta r)$

Since the incident medium is air thus we have $n_(1)=1$

By definition of refractive index we have

$n=(c)/(v)$

c = speed of light in vacuum

v = speed of light in medium

Applying values we get

$n_(2)=(3* 10^(8))/(2.5* 10^(8))=1.2$

Thus using the calculated values in Snell's law we obtain

$sin(\theta _(r))=(sin(31.3)/(1.2)\n\n\therefore sin(\theta _(r))=0.4329\n\n\theta_(r)=sin^(-1)(0.4329)\n\n\theta _(r)=29.14$

Answer:

Angle made by the transmitted ray = 25.65°

Explanation:

Speed of light in plastic = v = 2.5 × 10⁸ m/s

refractive index of plastic (n₂) / refractive index of air (n₁)

= speed of light in air c / speed of light in plastic v.

⇒ n₂ = (3× 10⁸) / (2.5 × 10⁸) = 1.2

Angle of incidence = 31.3° = i

n₁ sin i = n₂ sin r

⇒ sin r = (1)(0.5195) / 1.2 = 0.4329

⇒ Angle made by the transmitted ray = r = sin⁻¹ (0.4329) =25.65°

Exposure to what type of radiant energy is sensed by human skin as warmth? x-rays ultraviolet infrared gamma rays

Answers

infrared radiant energy is sensed by human skin as warmth. Hence option C is correct.

What is radiation ?

Radiation in physics is the emission or transmission of energy as waves, particles, or both, via space or a material medium.[1][2] This comprises:

electromagnetic radiation, which includes gamma radiation, x-rays, microwaves, infrared, visible light, and ultraviolet radiation

Particle radiation includes beta radiation, proton radiation, neutron radiation, and other particles with non-zero rest energies.

ultrasonography, sound, and seismic waves (reliant on a physical transmission medium) are examples of acoustic radiation.

gravity radiation, which manifests as gravitational waves or ripples in spacetime's curvature

Depending on the energy of the emitted particles, radiation is frequently divided into ionising and non-ionizing categories. More than 10 eV is carried by ionising radiation, which is sufficient to ionise atoms, molecules.

To know more about radiation :

brainly.com/question/13934832

#SPJ3.

i think it is infared

A 60kg woman on skates throws a 3.9kg ball with a velocity of37m.s west. What is the velocity of the woman?

Answers

Answer:

2.405 m/s

Explanation:

Given that,

Mass of a women, m₁ = 60 kg

Mass of a ball, m₂ = 3.9 kg

Velocity of the ball, v₂ = 37 m/s

We need to find the velocity of the woman. It is a concept based on the conservation of linear momentum. Let v₁ is the velocity of the woman. So,

$m_1v_1=m_2v_2\n\nv_1=(m_2v_2)/(m_1)\n\nv_1=(3.9* 37)/(60)\n\nv_1=2.405\ m/s$

So, the velocity of the woman is 2.405 m/s.

You observe three carts moving to the right. Cart A moves to the right at nearly constant speed. Cart B moves to the right, gradually speeding up. Cart C moves to the right, gradually slowing down. Which cart or carts, if any, experience a net force to the right

Answers

Answer:

Explanation:

Cart A is moving to the right with constant speed i.e. net acceleration is zero

because acceleration is change in velocity in given time

Cart B is moving towards right with gradually speed up so there is net acceleration which helps to increase the velocity s

This indicates the net force acting on the cart towards right

For cart C there is gradual slow down of cart which indicates cart is decelerating and a net force is acting towards which opposes its motion.

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