Which statement is true about how early humans met their needs?

During an extremely foggy day during the medieval era, an architect wants to determine the height of a building. He cannot see t

max2010maxim [7]

Answer:

Height of the building = 35.78 m

Explanation:

Given that,

The time period of a pendulum is, T = 12 s

We need to find the height of the building. The formula for the time period of a pendulum is given by :

$T=2\pi \sqrt{\dfrac{l}{g}}$

Where

l is the height of the building

$l=\dfrac{T^2g}{4\pi^2}\\\\l=\dfrac{(12)^2\times 9.8}{4\times 3.14^2}\\\\l=35.78\ m$

So, the height of the building is 35.78 m.

7 0

3 years ago

A water pump draws about 9 A when connected to 240 V. What is the cost (with electrical energy at 13 cents per kWh) of running t

Fiesta28 [93]

Answer:

4.49 dollars

Explanation:

i = 9 A, V = 240 V, t = 16 h

Energy = V x i x t = 240 x 9 x 16 = 34560 W h = 34.56 kWh

The cost of 1 kWh is 13 cents.

Cost of 34.56 kWh = 13 x 34.56 = 449.28 cents = 449.28 / 100 = 4.49 dollars

8 0

4 years ago

A high-jumper, having just cleared the bar, lands on an air mattress and comes to rest. Had she landed directly on the hard grou

Hoochie [10]

Answer:

e. the air mattress exerts the same impulse, but a smaller net avg force, on the high-jumper than hard-ground.

Explanation:

This is according to the Newton's second law and energy conservation that the force exerted by the hard-ground is more than the force exerted by the mattress.

The hard ground stops the moving mass by its sudden reaction in the opposite direction of impact force whereas the mattress takes a longer time to stop the motion of same mass in a longer time leading to lesser average reaction force.

Mathematical expression for the Newton's second law of motion is given as:

$F=\frac{dp}{dt}$ ............................................(1)

where:

dp = change in momentum

dt = time taken to change the momentum

We know, momentum:

$p=m.v$

Now, equation (1) becomes:

$F=\frac{d(m.v)}{dt}$

∵mass is constant at speeds v << c (speed of light)

$\therefore F=m.\frac{dv}{dt}$

and, $\frac{dv}{dt} =a$

where: a = acceleration

$\Rightarrow F=m.a$

also

$F\propto \frac{1}{dt}$

so, more the time, lesser the force.

& Impulse:

$I=F.dt$

$I=m.a.dt$

$I=m.\frac{dv}{dt}.dt$

$I=m.dv=dp$

∵Initial velocity and final velocity(=0), of a certain mass is same irrespective of the stopping method.

So, the impulse in both the cases will be same.

4 0

3 years ago

The total amount of water on earth_____. Remains the same. Is decreasing Is increasing

Elena L [17]

The total amount of water on earth remains the same.

Option: A

Explanation:

The quantity of water on Earth remains the same now as it was in the Olden days. All water which is consumed by living things continue to be as part of the Earth's total water content.

The total amount is not exactly constant, as there are two fluxes of water between Earth and the rest of the solar system. There is a steady rain of water-bearing meteoroids hitting the planet, which slowly increases the amount of water. At the same time, molecules of water often dissociate in the upper atmosphere into hydrogen and oxygen due to ultraviolet light from the sun. Some of the hydrogen atoms have enough energy to escape from Earth’s gravitational field, and so are lost. This slowly decreases the amount of water. In addition, tectonic plate subduction is constantly carrying water down into Earth’s mantle, and volcanoes are constantly spewing water out onto the surface again. The balance between the two processes can change considerably over time. But all of these actions are meager compared to the total quantity of water on our planet, and two of them are in the opposite direction of the other two. So the overall change is insignificant, even when considered over long spans of geologic time.

7 0

3 years ago

Read 2 more answers

Using a diagram explain how acceleration can be obtained from a velocity time graph

Oksi-84 [34.3K]

Answer:

For any v-t graph the acceleration is the slope of the graph. For average acceleration in a time period ‘t’ consider the change in velocity in time t and divide it by the time t. For instantaneous acceleration you need to go into the realm of differential calculus.

Explanation:

I hope this helps! I would really appreciate it if you would please mark me brainliest! Have a blessed day!

3 0

3 years ago