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2 years ago

A student lifts a 90 pound (lb) ball 4 feet (ft) in 5 seconds (s). How many joules of work has the student completed?

1 answer:

7 0

Wending your way through this question and the list of choices
is like running through a corn-maze on a moonless night with
your eyes closed.

Work = (force) x (distance)

Keeping with the units used In the question ...

   Work = (90 pounds) x (4 feet) = 360 foot-pounds .

If you want the work expressed in joules, then you need to convert
pounds and feet to newtons and meters.

   (90 pounds) x (4.448 newtons/pound) = 400.32 Newtons

   (4 feet) x (1 meter / 3.28084 feet) = 1.219 meters

Work = (force) x (distance)

      = (400.32 newtons) x (1.219 meters) = 488.1 joules .

You might be interested in

Two in-phase loudspeakers that emit sound with the same frequency are placed along a wall and are separated by a distance of 2.4

NeX [460]

When person is observing destructive interference at 0.20 m distance from the equidistant position then we can say that path difference must be equal to half of the wavelength

now we will have

$\frac{\lambda}{2} = \frac{yd}{L}$

now we know that

y = 0.20 m

d = 2.4 m

L = 10 m

now here we have

$\frac{\lambda}{2} = \frac{0.20\times 2.4}{10}$

$\lambda = 0.096 m$

now frequency of wave is given as

$f = \frac{v}{\lambda}$

$f = \frac{343}{0.096} = 3573 Hz$

5 0

3 years ago

A large lightning bolt is observed to have a 19500 A current and move 36 C of charge. What was its duration?

Lynna [10]

Answer:

Its duration is 1.85*10⁻³ s or 1.85 ms

Explanation:

The intensity of electric current I is defined as the amount of electric charge Q (measured in Coulombs) that passes through a section of a conductor in each unit of time. The letter I is used to name the Intensity and its unit is the Ampere (A).

The intensity of electric current is expressed as:

$I=\frac{Q}{t}$

where:

I: Intensity expressed in Amps (A)

Q: Electric charge expressed in Coulombs (C)

t: Time expressed in seconds (s)

Being:

I= 19500 A
Q=36 C
t=?

Replacing:

$19500 A=\frac{36 C}{t}$

Solving:

19500 A*t= 36 C

$t=\frac{36 C}{19500 A}$

t= 1.85*10⁻³ s= 1.85 ms (being 1 s= 1,000 ms)

Its duration is 1.85*10⁻³ s or 1.85 ms

8 0

2 years ago

Earth is about 150 million kilometers from the Sun, and the apparent brightness of the Sun in our sky is about 1300 watts/m2. Us

nalin [4]

Answer:

$13 W/m^2$

Explanation:

The apparent brightness follows an inverse square law, therefore we can write:

$I \propto \frac{1}{r^2}$

where I is the apparent brightness and r is the distance from the Sun.

We can also rewrite the law as

$\frac{I_2}{I_1}=\frac{r_1^2}{r_2^2}$ (1)

where in this problem, we have:

$I_1 = 1300 W/m^2$ apparent brightness at a distance $r_1$ , where

$r_1 = 150$ million km

We want to estimate the apparent brightness at $r_2$ , where $r_2$ is ten times $r_1$ , so

$r_2 = 10 r_1$

Re-arranging eq.(1), we find $I_2$ :

$I_2 = \frac{r_1^2}{r_2^2}I_1 = \frac{r_1^2}{(10r_1)^2}(1300)=\frac{1}{100}(1300)=13 W/m^2$

5 0

2 years ago

When a cannon is fired, how does the size of the force of the cannon on the cannonball compared with the force of the cannonball

kati45 [8]

The force applied to the cannonball and cannon is equal. The explosion inside the cannon will generate a pressure which will turn into a force on both cannonball and cannon. The cannon being heavier and fixed to the ground will move a bit, but the cannonball will be thrown away, fired.

3 0

3 years ago

iron ball weight 400 gram inside water when it is completely impressed in water 53 gram water is displaced what will be the weig

Alika [10]

Answer:

453 gm

Explanation:

Immersed objects are buoyed up by force equal to mass of displaced liquid

400 + 53 = 453 gm in air

8 0

1 year ago