1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
azamat
3 years ago
8

A 60-kg woman runs up a staircase 15 m high (vertically) in 20 s.

Physics
1 answer:
erma4kov [3.2K]3 years ago
4 0

Answer:

(a) 441 W (b) 0.59 hP

Explanation:

Given that,

Mass of a woman, m = 60 kg

Height of a staircase, h = 15 m

Time, t = 20 s

(a) We need to find the power she expend. Work done per unit time is called power. It is given by :

P=\dfrac{W}{t}\\\\P=\dfrac{mgh}{t}\\\\P=\dfrac{60\times 9.8\times 15}{20}\\\\P=441\ W

( b) Since, 1 hP = 745.7 W

P = 0.59 hP

You might be interested in
Two pith balls hang side by side close to each other without touching as shown in the figure below. They are both neutral to beg
Mila [183]

a)

When a plastic rod is rubbed with wool, charging by friction occurs.

This is one of the three mechanisms of charging an object: in this particular case, as the rod is rubbed with the wool, electrons jump from the wool to the rod.

As a result, the plastic rod will remain with an excess of electrons (negative charge), while the wool will remain with a lack of electrons (positive charge).

However, the number of electrons gained by the rod is equal to the number of electrons given off by the wool: therefore, the total net charge of the system rod + cloth has not changed.

b)

When the rod touches sphere A, some electrons are transferred from the rod to the sphere (this method of charging is called charging by conduction).

Then, the sphere A will also remain negatively charged, as well as the plastic rod.

Later, the rod is brought close to sphere A without touching it: here, the electrons in the rod repel the electrons in the sphere (like charges repel each other), so the rod and the sphere will repel each other.

c)

Before part b), the negative charge on the plastic rod was equal to the positive charge on the wool.

After part b), the plastic rod has given off part of its electrons to sphere A. As a result, the negative charge on the plastic rod will be now less than the positive charge on the wool.

Therefore, the net charge of the rod + wool system will now be positive.

d)

The electrostatic force between two charged object is:

- Attractive if the charges on the objects have opposite sign

- Repulsive if the charges on the objects have same sign

Since sphere A is charged negatively, when it is brought close to sphere B, the electrons in sphere B will be attracted on the opposite side relative to sphere A, while the positive charges will migrate close to sphere A. Therefore, the two spheres will attract each other, since opposite charges attract each other.

e)

When the plastic rod (which is negatively charged) touches sphere B, some electrons are transferred to sphere B (charging by induction). As a result, charge B will also be negatively charged now, as it has an excess of electrons.

At the same time, sphere A is also negatively charged. Therefore, as like charges repel each other, this means that the two spheres will now repel each other.

f)

The net charge of the rod and the two spheres is negative.

In fact, the electrons given off by the rod to the two spheres were initially on the rod itself: this means that the total net charge of the rod + 2 spheres is equal to the net charge on the rod before the process.

Since the net charge on the rod before the process was negative, then the net charge of the system consisting of the rod + 2 spheres must be negative as well.

g)

When a glass rod is rubbed with silk, charging by friction occurs, similar to part a). However in this case, the glass rod gives off electrons to the silk: therefore, the glass rod remains positively charged.

Later, the glass rod touches sphere B: as a result, positive charge is transferred from the rod to sphere B, so sphere B will remain positively charged.

In the meantime, sphere A is negatively charged: since opposite charges attract each other, this means that now sphere A and sphere B will attract each other.

h)

When the two spheres are moved a bit further apart, the attractive force between them decreases a bit. In fact, the electrostatic force between two charged objects is given by

F=k\frac{q_1 q_2}{r^2}

where

k is the Coulomb's constant

q1, q2 are the  charges on the two objects

r is the separation between the objects

As we can see, the force is inversely proportional to the square of the distance: therefore, if the separation between the spheres increases, the force will decrease.

4 0
2 years ago
Gina made a poster for plastic recycling week and included this information on her poster:
miskamm [114]

Answer:

Gina should put “rubber tires” under “Synthetic.”

Gina should put “starch” under “Natural.”

Explanation: I just did the assignment ;P

4 0
3 years ago
Read 2 more answers
1) Arrange the following spectral regions in order of increasing energy: infrared, microwave, ultraviolet, visible.
Anton [14]

Answer:

The order of increasing energy is as follows

"microwave < infrared < visible < ultraviolet"

Option (A) is correct.

Explanation:

Given:

Arrange the following spectral regions in order of increasing energy: infrared, microwave, ultraviolet, visible.

From the formula of energy in terms of frequency.

  E = hf

Where h = planck constant, f = frequency of light.

From above formula we can conclude that higher frequency means higher energy.

In our case ultraviolet has higher frequency and microwave has lower frequency.

So ultraviolet has higher energy and microwave has lower energy.

microwave < infrared < visible < ultraviolet

Therefore, the order of increasing energy is as follows

"microwave < infrared < visible < ultraviolet"

7 0
3 years ago
What is the proper way to start a fire?
Katyanochek1 [597]

Answer:

Explanation:

STEP 1: Gather Your Tools. There's a bit more to building a great campfire than simply placing a few logs in a heap ... If your site has a fire ring, you'll probably have to push the ash and charcoal from ... (Remember, tinder is the really light, quick burning material.) 1. ... Then build a larger teepee of firewood over the kindling.

6 0
3 years ago
The rate at which heat enters an air conditioned building is often roughly proportional to the difference in temperature between
erma4kov [3.2K]

Answer:

Considering first question

    Generally the coefficient of performance of the air condition  is mathematically represented as

   COP  =  \frac{T_i}{T_o - T_i}

Here T_i is the inside temperature

while  T_o is the outside temperature

What this coefficient of performance represent is the amount of heat the air condition can remove with 1 unit of electricity

So it implies that the air condition removes   \frac{T_i}{T_o - T_i} heat with 1 unit of electricity

Now from the question we are told that the rate at which heat enters an air conditioned building is often roughly proportional to the difference in temperature between inside and outside. This can be mathematically represented as

         Q \ \alpha \ (T_o - T_i)

=>        Q= k (T_o - T_i)

Here k is the constant of proportionality

So  

    since  1 unit of electricity  removes   \frac{T_i}{T_o - T_i}  amount of heat

   E  unit of electricity will remove  Q= k (T_o - T_i)

So

      E =  \frac{k(T_o - T_i)}{\frac{T_i}{ T_h - T_i} }

=>   E = \frac{k}{T_i} (T_o - T_i)^2

given that  \frac{k}{T_i} is constant

    =>  E \  \alpha  \  (T_o - T_i)^2

From this above equation we see that the  electricity required(cost of powering and operating the air conditioner) is approximately proportional to the square of the temperature difference.

 Considering the  second question

Assuming that  T_i   =  30 ^oC

 and      T_o  =  40 ^oC

Hence  

     E = K (T_o - T_i)^2

Here K stand for a constant

So  

        E = K (40 -  30)^2

=>      E = 100K

Now if  the  T_i   =  20 ^oC

Then

       E = K (40 -  20)^2

=>      E = 400 \ K

So  from this see that the electricity require (cost of powering and operating the air conditioner)when the inside temperature is low  is  much higher than the electricity required when the inside temperature is higher

Considering the  third question

Now in the case where the  heat that enters the building is at a rate proportional to the square-root of the temperature difference between inside and outside

We have that

       Q = k (T_o - T_i )^{\frac{1}{2} }

So

       E =  \frac{k (T_o - T_i )^{\frac{1}{2} }}{\frac{T_i}{T_o - T_i} }

=>   E =  \frac{k}{T_i} * (T_o - T_i) ^{\frac{3}{2} }

Assuming \frac{k}{T_i} is a constant

Then  

     E \ \alpha \ (T_o - T_i)^{\frac{3}{2} }

From this above equation we see that the  electricity required(cost of powering and operating the air conditioner) is approximately proportional to the square root  of the cube of the  temperature difference.

   

4 0
2 years ago
Other questions:
  • The left plate of a parallel plate capacitor carries a positive charge Q, and the right plate carries a negative charge -Q. The
    5·1 answer
  • Rutherford's atomic theory included which idea?
    13·1 answer
  • A water holding tank measures 85 m long, 55 m wide, and 9 m deep. Traces of mercury have been found in the tank, with a concen-
    9·1 answer
  • What do we call it when two or more moving objects exert forces on each other for a short period of time?​
    13·1 answer
  • __________________ have almost no mass. A.protons B.neutrons C.electrons D.atoms
    7·1 answer
  • When charges build up on a surface they:
    6·2 answers
  • A 5.0\, \text {kg}5.0kg5, point, 0, start text, k, g, end text box is at rest on a table. The static friction coefficient \mu_sμ
    11·2 answers
  • "1. Which properties make a metal a good material to use for electrical wires? (1 poi
    7·1 answer
  • For for each situation say how the ideas of force pressure and area can be applied :
    8·1 answer
  • If a car increases its velocity from +6 m/s to +30 m/s in 6 seconds, its acceleration in m/s2 is__________.
    7·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!