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4 years ago

A train is accelerating at a rate of 2 km/hr/s. If its initial velocity is 20 km/hr, what is its velocity after 30 seconds?

1 answer:

4 0

"2 km/hr/s" means that in each second, its engines can increase its speed by 2 km/hr.

If it keeps doing that for 30 seconds, its speed has increased by 60 km/hr.

On top of the initial speed of 20 km/hr, that's 80 km/hr at the end of the 30 seconds.

This whole discussion is of <em>speed</em>, not velocity. Surely, in high school physics,
you've learned the difference by now. There's no information in the question that
says anything about the train's <em>direction</em>, and it was wrong to mention velocity in
the question. This whole thing could have been taking place on a curved section
of track. If that were the case, it would have taken a team of ace engineers, cranking
their Curtas, to describe what was happening to the velocity. Better to just stick with
speed.

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Describe a line that indicates moving backward on a graph

Vladimir [108]

Answer:

time speed accelaration negatives backwards

Explanation:

4 0

3 years ago

How do you think television programs movies and car commercials influence driving behavior

AnnZ [28]

When you watch the same thing over and over (like a car commercial), then your brain begins to question morals. Like if you see a racing movie you might want to go and race. Or if you see an underage kid illegally driving, you might want to try it too.

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3 years ago

During a 40-mile trip, Marla traveled at an average speed of x miles per hour for the first y miles of the trip and at an averag

Ilya [14]

Answer:

$\dfrac{32+0.2y}{40}$

Explanation:

Total =40 miles.

y miles at x miles/hr.

40- y miles at 1.25 x miles/hr.\

We know that

Distance = time x velocity

For y miles

Lets time taken to cover y miles is t

y = x t

t=y/x -----------1

For 40- y

Lets time taken to cover 40- y is t'

40- y = 1.25 x t'

t'=(40-y)/1.25x -----------2

By adding both equation

t+t'=y/x + (40-y)/1.25x

t+t'=(32+0.2y)/x

Now lets time T taken by Marla if she will travel at x miles per hr for entire trip.

40 = x T

T=40/x

$\dfrac{t+t'}{T}=\dfrac{32+0.2y}{40}$

To find numerical value of above expression we have to know the value of y.

8 0

4 years ago

A 4-foot spring measures 8 feet long after a mass weighing 8 pounds is attached to it. The medium through which the mass moves o

aniked [119]

Correct question is;

A 4-foot spring measures 8 feet long after a mass weighing 8 pounds is attached to it. The medium through which the mass moves offers a damping force numerically equal to √2 times the instantaneous velocity. Find the equation of motion if the mass is initially released from the equilibrium position with a downward velocity of 7 ft/s. (Use g = 32 ft/s²)

Answer:

x(t) = 7te^(-2t√2)

Explanation:

We are given;

Weight; W = 8 lbs

mass; m = W/g

g = 32 ft/s²

Thus;

m = 8/32

m = ¼ slugs

From Newton's second law we can write the equation as;

m(d²x/dt²) = -kx - β(dx/dt)

Rearranging this, we have;

(d²x/dt²) + (β/m)(dx/dt) + (k/m)x = 0

Where;

β is damping constant = √2

k is spring constant = W/s

Where s = 8ft - 4ft = 4ft

k = 8/4

k = 2

Thus,we now have;

(d²x/dt²) + (√2/(¼))(dx/dt) + (2/(¼))x = 0

>> (d²x/dt²) + (4√2)dx/dt + 8x = 0

The auxiliary equation of this is;

m² + (4√2)m + 8 = 0

Using quadratic formula, we have;

m1 = m2 = -2√2

The general solution will be gotten from;

x_t = c1•e^(mt) + c2•t•e^(mt)

Plugging in the relevant values gives;

x_t = c1•e^(mt) + c2•t•e^(mt)

At initial condition of t = 0, x_t = 0 and thus; c1 = 0

Also at initial condition of t = 0, x'(0) = 7 and thus;

Since c1 = 0, then c2 = 7

Thus,equation of motion is;

x(t) = 7te^(-2t√2)

8 0

3 years ago

A ball falls from a height of 25 cm what is the same distance described in meters? Someone help ASAP THIS IS DO TONIGHT

posledela

.25 meters

divide the value by 100 to get your answer.

5 0

3 years ago

Read 2 more answers