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3 years ago

14

A ship was traveling across the Atlantic Ocean. It traveled 2,000 kilometers at a rate of 40 kilometers per hour. How long did i

t take the ship to travel this distance?
A.
0.02 hr
B.
40 hr
C.
50 hr
D.
80,000 hr

1 answer:

8_murik_8 [283]3 years ago

6 0

The correct answer is D

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A Russian athlete lifts 300kg to a height of 2.5 m in 2 seconds. What is the work done? And what power is exerted?

snow_tiger [21]

We want to find the work done and power exerted, let’s start with work first.

We know that the equation for work is: W = F * D. We need to find the force which we can find by using: F = M * A.

Mass: 300kg
Acceleration (using equation from photo): 1.25 m/s^2

(The equation says x but can be used with y values)

If you are confused about how I found the acceleration; I plugged in 2.5 for the final y value, 0 for the initial y value, 0 for the initial velocity and 4 for t squared.

To solve, for acceleration it’s a matter of simple algebra. You can subtract the initial y position and the initial velocity from the final y position because they are 0. This leaves you with 2.5 m = 1/2a * t^2, from here I multiplied 2.5 by 2 to get rid of the 1/2. Now I have 5 = a * t^2. T^2 is just 2 squared, so four. Simply divide 5 by 4, and boom, you get 1.25 m/s^2.

Force = 300 kg * 1.25 m/s^2 = 375 Newtons

So, work = 500 N * 2.5 m = 1000 Joules

Power: W/t

So, Power = 1000 J / 2 seconds = 500 Watts

Hope this helps!

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3 years ago

A uniform rod of mass M and length L can pivot freely at one end. Initially, the rod is oriented vertically above the pivot, in

Leya [2.2K]

Answer:

The speed of its center of mass = $\sqrt{\frac{3}{2}gL}$

Explanation:

Consider the potential energy at the level of center of mass of rod below the pivot=0

Mass of uniform rod=M

Length of rod=L

The rotational inertia about the end of a uniform rod= $\frac{1}{3}ML^2$

Kinetic energy at the level of center of mass of rod below the pivot= $\frac{1}{2}I\omega^2$

Kinetic energy at the level of center of mass of rod above the pivot=0

Potential energy at the level of center of mass of rod above the pivot=mgh

We have to find the center of mass ( in terms of g and L).

According to conservation of law of energy

Initial P.E+Initial K.E=Final P.E+Final K.E

$mgh+0=0+\frac{1}{2} I\omega^2$

Where $K.E=\frac{1}{2} I\omega^2$

I=Moment of inertia

$\omega$ =Angular velocity

Substitute the values then we get

$MgL=\frac{1}{2}\times \frac{1}{3}ML^2\omega^2$

$\omega^2=\frac{6g}{L}$

Now, we know that $\omega=\frac{v}{r}$ , $r=\frac{L}{2}$

Substitute the values then we get

$\frac{v^2}{(\frac{L}{2})^2}=\frac{6g}{L}$

$\frac{v^24}{L^2}=\frac{6g}{L}$

$v^2=\frac{6g\times L^2}{4L}$

$v^2=\frac{3gL}{2}$

$v=\sqrt{\frac{3}{2}gL}$

Hence, the speed of its center of mass = $\sqrt{\frac{3}{2}gL}$

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4 years ago

Two fish swimming in a river have the following equations of motion:

IRINA_888 [86]

Answer:

The second fish, X2, is moving faster than the first fish, X1

Explanation:

The given parameters for the equation of motion of the fishes are;

X1 = -6.4 m + (-1.2 m/s)×t

X2 = 1.3 m + (-2.7 m/s)×t

The given equation are straight line equations in the slope and intercept form, where the slope is the speed and in m/s and the intercept is the starting point of swimming of the fishes

For the first fish, the intercept = -6.4 m, the slope = the speed = -1.2 m/s

For the second fish, the intercept = 1.3 m, the slope = the speed = -2.7 m/s

Whereby the fishes are swimming in the opposite direction of the measurement of length, we have;

The magnitude of the speed of the second fish $\left | -2.7 \ m/s \right | = 2.7 \ m/s$ , is larger than the magnitude of the speed of the first fish $\left | -1.2 \ m/s \right | = 1.2 \ m/s$

Therefore, the second fish, X2, is moving faster than the first fish, X1.

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3 years ago

A 10.0 cm3 sample of copper has a mass of 89.6

Romashka-Z-Leto [24]

Density is mass divides by volume, so
89.6g / 10cm^3 =8.96g /cm^3

*cm^3 is a standard unit of volume*

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4 years ago

Before leaving her home, Myesha makes sure that every electrical appliance is unplugged and checks that every window and door is

Kryger [21]

Answer:Obsessive-Compulsive Disorder

Explanation:

Obsessive-Compulsive Disorder is a general, persistent, and soon-lasting disorder in which an individual has involuntary, repetitive thoughts and/or actions that he or she feels compelled to replicate over and over.

Myesha also shows the symptoms of OCD by constantly checking the window and doors.

An individual suffering from OCD shows symptoms like

Fear of or infection by germs
Aggressive feelings to others or self
Getting things in a symmetrical or optimal order

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3 years ago