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AnnyKZ [126]
3 years ago
13

An engineer in a locomotive sees a car stuck on the track at a railroad crossing in front of the train . When the engineer first

sees the car, the locomotive is 110 m from the crossing and its speed is 21 m/s . If the engineer's reaction time is 0.6 s, what should be the magnitude of the minimum de celeration to avoid an accident ? Answer in units of m/s^ 2
Physics
1 answer:
8_murik_8 [283]3 years ago
4 0

Answer:

Explanation:

distance traveled during reaction time

d = vt = 21(0.6) = 12.6 m

distance remaining 110 - 12.6 = 97.4 m

Assuming we want zero speed in 97.4 m using constant acceleration.

a = (0² - 21²) / 2(97.4) = - 2.2638603...

the negative value indicates acceleration opposes initial velocity.

magnitude is

a = 2.3 m/s²

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A major-league pitcher can throw a ball in excess of 40.1 m/s. If a ball is thrown horizontally at this speed, how much will it
mote1985 [20]

Answer:

The ball will drop 0.881 m by the time it reaches the catcher.

Explanation:

The position of the ball at time "t" is described by the position vector "r":

r = (x0 + v0x · t, y0 + v0y · t + 1/2 · g · t²)

Where:

x0 = initial horizontal position.

v0x = initial horizontal velocity.

t = time.

y0 = initial vertical position.

v0y = initial vertical velocity.

g = acceleration due to gravity (-9.8 m/s² considering the upward direction as positive).

When the ball reaches the catcher, the position vector will be "r final" (see attached figure).

The x-component of the vector "r final", "rx final", will be 17.0 m. We have to find the y-component.

Using the equation of the x-component of the position vector, we can calculate the time it takes the ball to reach the catcher (notice that the frame of reference is located at the throwing point so that x0 and y0 = 0):

x = x0 + v0x · t

17.0 m = 0 m + 40.1 m/s · t

t = 17.0 m/ 40. 1 m/s = 0.424 s

With this time, we can calculate the y-component of the vector "r final", the drop of the ball:

y = y0 + v0y · t + 1/2 · g · t²

Initially, there is no vertical velocity, then, v0y = 0.

y = 1/2 · g · t²

y = -1/2 · 9.8 m/s² · (0.424 s)²

y = -0.881 m

The ball will drop 0.881 m by the time it reaches the catcher.

8 0
3 years ago
1.What type of sediment forms from minerals that crystallize from seawater?
nikdorinn [45]
The correct answers are as follows:
<span>1) hydrogenous sediment

2)sand and gravel

3) They rapidly break down at surface temperatures and pressures.</span>
7 0
3 years ago
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Describes the relationship between the spectrum of one atom and the spectrum of another?
krok68 [10]

The relationship between the number of visible spectral lines are identical for atoms .However they have unique wavelengths.

Option B

<u> Explanation:</u>

A spectrum is a range of frequencies or a range of wavelengths. The photon energy of the emitted photon is equal to the difference between two states. For every atom there are quite many electron transitions and each has a energy difference.

This difference in wavelength causes spectrum .As each element emission spectrum is unique because each atom has different energy and causes uniqueness in the emission spectrum . Hence, due to the difference in energy it emits different wavelengths.

6 0
3 years ago
Explain why objects moving in fluids must have special shapes ?
Alexus [3.1K]

Explanation:

Fluids exert both drag and lift forces on moving objects.  Drag is the frictional force opposing motion.  Lift is the force perpendicular to motion.

Some objects, like parachutes, are designed with large cross sectional areas to increase drag force.  Usually though, objects are designed to minimize drag force.  It's why cars, planes, and boats have sleek shapes.

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8 0
3 years ago
A pendulum consists of a large balanced mass hanging on the end of a long wire. At the point where a 28-kg pendulum has the grea
Ray Of Light [21]

Answer:

The length of the wire is approximately 67.1 m

Explanation:

The parameters of the pendulum are;

The mass of the pendulum, m = 28 kg

The angle between the pendulum weight and the wire, θ = 89°

The magnitude of the torque exerted by the pendulum's weight, τ = 1.84 × 10⁴ N·m

We have;

Torque, τ = F·L·sinθ = m·g·l·sinθ

Where;

F = The applies force = The weight of the pendulum = m·g

g = The acceleration due to gravity ≈ 9.8 m/s²

l = The length of the wire

Plugging in the values of the variables gives;

1.84 × 10⁴ N·m = 28 kg × 9.8 m/s² × l × sin(89°)

Therefore;

l = 1.84 × 10⁴ N·m/(28 kg × 9.8 m/s² ×  sin(89°)) = 67.0656080029 m ≈ 67.1 m

The length of the wire, l ≈ 67.1 m

6 0
3 years ago
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