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julsineya [31]
3 years ago
7

in which activity is no work done? A. pushing a shopping cart B. climbing stairs C. holding a brick D. lifting a book

Physics
1 answer:
Vesnalui [34]3 years ago
3 0
Your answer is c holding a brick doesn't contain movement, but energy to grip on it.

hoped it helped!!!
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Can anyone please explain this point with an example. I have presentation tomorrow.
r-ruslan [8.4K]

Explanation:

Efficiency is a way of describing the amount of useful ​output​ a process or machine can generate as a percentage of the ​input​ required to make it go. In other words, it compares how much energy is used to do work versus how much is lost or wasted to the environment. The more efficient the machine, the less energy wasted.

For example, if a heat engine is able to turn 75 percent of the fuel it receives into motion, while 25 percent is lost as heat in the process, it would be 75 percent efficient. Out of the original 100 percent of the fuel, 75 percent was output as useful work.  

the equation:

energy efficiency =useful output energy/total input energy

8 0
2 years ago
Flowchart symbols
MArishka [77]

Answer:

Option (A)

Explanation:

A flowchart can be described as a representation of a process or an algorithm in a sequential manner (stepwise) in the form of diagrams. These steps are made of symbols that are connected to one another with the help of arrows. These arrows are used to show the direction of the process.  

There are mainly four symbols that are used to describe a flow chart, which includes-

  • Oval or Pill Shape- This type of symbol is used to depict the start or the end of a process.
  • Rectangle Shape- This type of symbols is used to describe the process .
  • Diamond Shape- This type of symbol is used to represent decision s.
  • Parallelogram- This type of symbol is used for the representation of an input or an output.

Thus, the correct answer is option (A).

5 0
3 years ago
Fruits and vegetables should take up half you plate at a meal.<br> A. <br> True<br> B. <br> False
umka21 [38]

Answer:

A. true

Explanation:

3 0
2 years ago
Read 2 more answers
A 175-kg roller coaster car starts from rest at the top of an 18.0-m hill and rolls down the hill, then up a second hill that ha
Anni [7]

Answer:

The work done by non-conservative forces on the car from the top of the first hill to the top of the second hill is 6574.75 joules.

Explanation:

By Principle of Energy Conservation and Work-Energy Theorem we present the equations that describe the situation of the roller coaster car on each top of the hill. Let consider that bottom has a height of zero meters.

From top of the first hill to the bottom

m\cdot g \cdot h_{1} = \frac{1}{2}\cdot m\cdot v_{1}^{2} +W_{1, loss} (1)

From the bottom to the top of the second hill

\frac{1}{2}\cdot m\cdot v_{1}^{2} = m\cdot g \cdot h_{2} + \frac{1}{2}\cdot m \cdot v_{2}^{2}+W_{2,loss} (2)

Where:

m - Mass of the roller coaster car, in kilograms.

v_{1} - Speed of the roller coaster car at the bottom between the two hills, in meters per second.

g - Gravitational acceleration, in meters per square second.

h_{1} - Height of the first top of the hill with respect to the bottom, in meters.

W_{1, loss} - Work done by non-conservative forces on the car between the top of the first hill and the bottom, in joules.

v_{2} - Speed of the roller coaster car at the top of the second hill, in meters per seconds.

h_{2} - Height of the second top of the hill with respect to the bottom, in meters.

W_{2, loss} - Work done by non-conservative forces on the car bewteen the bottom between the two hills and the top of the second hill, in joules.

By using (1) and (2), we reduce the system of equation into a sole expression:

m\cdot g\cdot h_{1} = m\cdot g\cdot h_{2} + \frac{1}{2}\cdot m \cdot v_{2}^{2} + W_{loss} (3)

Where W_{loss} is the work done by non-conservative forces on the car from the top of the first hill to the top of the second hill, in joules.

If we know that m = 175\,kg, g = 9.807\,\frac{m}{s^{2}}, h_{1} = 18\,m, h_{2} = 8\,m and v_{2} = 11\,\frac{m}{s}, then the work done by non-conservative force is:

W_{loss} = m\cdot\left[ g\cdot \left(h_{1}-h_{2}\right)-\frac{1}{2}\cdot v_{2}^{2} \right]

W_{loss} = 6574.75\,J

The work done by non-conservative forces on the car from the top of the first hill to the top of the second hill is 6574.75 joules.

8 0
2 years ago
What is the change in momentum of a 50-kg rock that falls freely for 3 seconds?
Elan Coil [88]

Answer:

1470kgm/s

Explanation:

Given parameters:

Mass of the rock = 50kg

Time taken for the free fall  = 3s

Unknown:

Change in momentum = ?

Solution:

The change in momentum will be difference between the ending momentum and finishing momentum.

  Momentum is the product of mass and velocity

       Momentum  = mass x velocity

Initial momentum  = 0, the velocity is 0

Final momentum = mass x final velocity

      let us find the final velocity;

                V = U + gt

V is the final velocity

U is the initial velocity

g is the acceleration due to gravity = 9.8m/s²

t is the time

                 V  = 0 + 9.8x3 = 29.4m/s

So;

 Change in momentum  = 50 x 29,4  = 1470kgm/s

6 0
3 years ago
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