Is work being done on a barbell when a weight lifter is holding the barbell<br> over his head?

Anvisha [2.4K]

The speed of the rock at 20 m is 34.3 m/s

Explanation:

We can solve this problem by using the law of conservation of energy: the mechanical energy of the rock, sum of its potential energy + its kinetic energy) must be conserved in absence of air resistance. So we can write:

$U_i +K_i = U_f + K_f$

where :

$U_i$ is the initial potential energy

$K_i$ is the initial kinetic energy

$U_f$ is the final potential energy

$K_f$ is the final kinetic energy

The equation can also be rewritten as follows:

$mgh_i + \frac{1}{2}mu^2 = mgh_f + \frac{1}{2}mv^2$

where:

m = 100 kg is the mass of the rock

$g=9.8 m/s^2$ is the acceleration of gravity

$h_i = 80$ is the initial height

u = 0 is the initial speed (the rock starts at rest)

$h_f = 20 m$ is the final height of the rock

v is the final speed when h = 20 m

And solving for v, we find:

$v=\sqrt{2g(h_i-h_f)}=\sqrt{2(9.8)(80-20)}=34.3 m/s$

Learn more about kinetic energy and potential energy here:

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5 0

3 years ago

Which of the following units would need to be converted before being used for a calculation

Andreyy89

The units which would need to be converted before being used for a calculation are cm and 0 ks.

This is referred to a standard which is used to make comparisons in the aspect of measurement.

The units cm and 0 ks aren't in their standard form which is m and s respectively.

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6 0

1 year ago

Find the position of the center of mass of the system of the sun and Jupiter? (Since Jupiter is more massive than the rest of th

8090 [49]

Answer:

$r_{cm} = 0.074 m$ from the position of the center of the Sun

Explanation:

As we know that mass of Sun and Jupiter is given as

$M_s = 1.98 \times 10^{30} kg$

$M_j = 1.89 \times 10^{27} kg$

distance between Sun and Jupiter is given as

$r = 7.78 \times 10^{11} m$

now let the position of Sun is origin and position of Jupiter is given at the position same as the distance between them

so we will have

$r_{cm} = \frac{M_s r_1 + M_j r_2}{M_s + M_j}$

$r_{cm} = \frac{1.98 \times 10^{30} (0) + (1.89 \times 10^{27})(7.78 \times 10^{11})}{1.98 \times 10^{30} + 1.89 \times 10^{27}}$

$r_{cm} = 0.074 m$ from the position of the center of the Sun

3 0

3 years ago

A tiger is running across a field. What would happen if the hydrogen ion pumps into the tigers mitochondria stopped functioning

galben [10]

Answer:

The tiger would not be able to produce glucose causing it to stop running

Explanation:

Since the mitochondria is in charge of producing ATP the tiger would not be able to use any glucose causing it to not be able to run.

3 0

3 years ago

From January 26, 1977, to September 18, 1983, George Meegan of Great Britain walked from Ushuaia, at the southern tip of South A

Nikolay [14]

Answer:

0.146 m/s

Explanation:

We can see it in the pic.

3 0

3 years ago

Is work being done on a barbell when a weight lifter is holding the barbell over his head?