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3 years ago

A train moves from rest to a speed of 25 m/s in 30.0 seconds. What is its acceleration?

Physics

1 answer:

iris [78.8K]3 years ago

4 0

Answer:

Explanation:

The equation for acceleration is

$a=\frac{v_f-v_0}{t}$ where vf is the final velocity and v0 is the initial velocity. For us, the final velocity is 25 m/s and the initial is 0 because the train started from resting position. Filling in and solving for a:

$a=\frac{25-0}{30.0}$ so

a = .83 m/s/s

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An object is accelerating from rest at a rate of 3 m/s2.How long will it take the object to attain 18 m/s ? *

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Initial velocity =0, a=3m/s2, final velocity =18m/s, 18=3t, t=6 sec

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3 years ago

You stand on a bridge above a river and drop a rock into the water below from a height of 25 m. (Assume no air resistance)

Ilia_Sergeevich [38]

PART a)

here when stone is dropped there is only gravitational force on it

so its acceleration is only due to gravity

so we will have

$a = g = 9.8 m/s^2$

Part b)

Now from kinematics equation we will have

$y = v_i t + \frac{1}{2} at^2$

now we have

y = 25 m

so from above equation

$25 = 0 + \frac{1}{2}(9.8 )t^2$

$t = 2.26 s$

Part c)

If we throw the rock horizontally by speed 20 m/s

then in this case there is no change in the vertical velocity

so it will take same time to reach the water surface as it took initially

So t = 2.26 s

Part D)

Initial speed = 20 m/s

angle of projection = 65 degree

now we have

$v_x = vcos\theta$

$v_x = 20 cos65 = 8.45 m/s$

$v_y = vsin\theta$

$v_y = 20 sin65 = 18.13 m/s$

PART E)

when stone will reach to maximum height then we know that its final speed in y direction becomes zero

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$v_f - v_y = at$

$0 - 18.13 = (-9.8) t$

$t = 1.85 s$

so it will take 1.85 s to reach the top

5 0

3 years ago

Please help i’m running out of time to answer

kipiarov [429]

Answer:

5,970 N

Explanation:

m = 597 kg

a = 10 m/s^2

Plug those values into the following equation:

F = ma

F = (597 kg)(10 m/s^2)

F = 5,970 N

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3 years ago

Suppose a car travels 108 km at a speed of 30.0 m/s, and uses 1.90 gallons of gasoline. Only 30% of the gasoline goes into usefu

Aleksandr [31]

Answer:

686.11 N

1.7733 gallons

Explanation:

$\eta$ = Efficiency = 30%

V = Volume of gasoline

E = Energy content of gasoline = $1.3\times 10^8\ J/gal$

F = Force

s = Displacement = 108000 m

v = Velocity

Work done is given by

$W=F\times s\\\Rightarrow F=\frac{W}{s}\\\Rightarrow F=\frac{VE\eta}{s}\\\Rightarrow F=\frac{1.9\times 0.3\times 1.3\times 10^8}{108000}\\\Rightarrow F=686.11\ N$

The force required to keep the car moving at a constant speed is 686.11 N

Here the force is directly proportional to speed

$\\\Rightarrow F=v$

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The gallons that will be used is 1.7733 gallons

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Burka [1]

Answer:

Explanation:

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3 years ago

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