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3 years ago

Think about a girl on a swing. When is the kinetic energy of the girl zero?

2 answers:

7 0

Kinetic energy is energy of motion. Pick choice-A, at the top of the swing, where she stops moving & then goes the other way.

tiny-mole [99]3 years ago

6 0

<h2>Answer:</h2>

<u>The K.E is zero</u><u> when she stops moving at the top of the swing </u>

<h2>Explanation:</h2>

Kinetic energy is the energy produced by the motion of the object and when the object is not moving so we consider the kinetic energy as zero. When the girl swings and the swing reaches its top point, it stops for a moment and then comes back so the point where the swing stops moving the kinetic energy is zero.

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A spherical balloon has a radius of 7.40 m and is filled with helium. Part A How large a cargo can it lift, assuming that the sk

malfutka [58]

Answer:

The mass of the cargo is $M = 188.43 \ kg$

Explanation:

From the question we are told that

The radius of the spherical balloon is $r = 7.40 \ m$

The mass of the balloon is $m = 990\ kg$

The volume of the spherical balloon is mathematically represented as

$V = \frac{4}{3} * \pi r^3$

substituting values

$V = \frac{4}{3} * 3.142 *(7.40)^3$

$V = 1697.6 \ m^3$

The total mass the balloon can lift is mathematically represented as

$m = V (\rho_h - \rho_a)$

where $\rho_h$ is the density of helium with a value of

$\rho_h = 0.179 \ kg /m^3$

and $\rho_a$ is the density of air with a value of

$\rho_ a = 1.29 \ kg / m^3$

substituting values

$m = 1697.6 ( 1.29 - 0.179)$

$m = 1886.0 \ kg$

Now the mass of the cargo is mathematically evaluated as

$M = 1886.0 - 1697.6$

$M = 188.43 \ kg$

5 0

3 years ago

An airplane takes off a runway at a constant speed of 49m/s at constant angle 30 to the horizontal

joja [24]

Complete Question

An airplane takes off a runway at a constant speed of 49 m/s at constant angle 30 to the horizontal.How high (in meters ) is the airplane above the ground 13 seconds after takeoff?

Answer:

The height is $H = 318.5 \ m$

Explanation:

From the question we are told that

The speed at which the plane takes off is $u = 49 \ m/s$

The angle at which it takes off is $\theta = 30 ^o$

The time taken is $t = 13 s$

The vertical distance traveled is mathematically represented as

$H = u sin \theta t$

Substituting values

$H = (49) * sin (30) *13$

$H = 318.5 \ m$

6 0

3 years ago

Sandy is whirling a ball attached to a string in a horizontal circle over his head. If Sandy doubles the speed of the ball, what

jeka57 [31]

The tension in the string B) It quadruples.

Explanation:

The ball is in uniform circular motion in a horizontal circle, so the tension in the string is providing the centripetal force that keeps the ball in circular motion. So we can write:

$T= m\frac{v^2}{r}$