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2 years ago

11

Energy Calculation 4. What is the gravitational potential energy of an object that has a mass of 100kg it is 10m off of the grou

nd? The gravity on Earth is measured at 9.8N/kg

1 answer:

konstantin123 [22]2 years ago

3 0

100kg * 9.8N/kg * 10m = 9800

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A skateboarder is skating back and forth on the halfpipe as seen below. As he skates his energy transforms from potential energy

egoroff_w [7]

Answer:

Friction and air resistance cause some of his kinetic energy to be “lost”. This makes him slow down.

Explanation:

The law of conservation of energy states that in absence of frictional forces, the mechanical energy of an object (given by the sum of its kinetic and potential energy) is conserved. In such a situation, the skateboarder would never stop his motion, because potential energy is continuously converted into kinetic energy and vice-versa, but the total energy remains the same so he would never stop.

In a real world, however, this is not true. In fact, in a real world some frictional force are present, in particular:

- friction: this force is due to the contact between the skateboard and the surface of the halfpipe, and its direction is always opposite to the motion of the skateboarder

- Air resistance: this force is due to the resistance opposed by the molecules of air that the skateboarder meets during his motion, and its direction is also opposite to the motion of the skateboarder

This two forces are said to be non-conservative forces, which means that they cause some of the mechanical energy of the skateboarder to be "lost", in the sense that it is dissipated as heat and it is no longer available for the skateboarder.

Therefore, the correct option is

Friction and air resistance cause some of his kinetic energy to be “lost”. This makes him slow down.

7 0

3 years ago

What frequency fapproach is heard by a passenger on a train moving at a speed of 18.0 m/s relative to the ground in a direction

Sergio039 [100]

Answer:

The frequency is 302.05 Hz.

Explanation:

Given that,

Speed = 18.0 m/s

Suppose a train is traveling at 30.0 m/s relative to the ground in still air. The frequency of the note emitted by the train whistle is 262 Hz .

We need to calculate the frequency

Using formula of frequency

$f'=f(\dfrac{v+v_{p}}{v-v_{s}})$

Where, f = frequency

v = speed of sound

$v_{p}$ = speed of passenger

$v_{s}$ = speed of source

Put the value into the formula

$f'=262\times(\dfrac{344+18}{344-30})$

$f'=302.05\ Hz$

Hence, The frequency is 302.05 Hz.

7 0

3 years ago

In an HVAC system, the purpose of pneumatics is to serve as A. a controller B. conditional air flow C. an energy source D. a sou

Naya [18.7K]

Answer: <u><em>A</em></u>

Explanation:

A pneumatic control system uses compressed air as a method of control for HVAC systems. ... Each senor responds to changes in temperature, humidity, and static pressure as examples, to provide feedback in a control loop to open or close the actuator to meet the control set point.

3 0

3 years ago

How did doubling the pressure change the gas volume?

stiv31 [10]

<span>For an ideal gas, the product of pressure and volume equals a constant times the absolute temperature. If each of the temperature and pressure of the gas is doubled, the product of pressure and volume increases by a factor of 4, and the absolute temperature must increase by the same ratio.</span>

7 0

3 years ago

A ball rolls onto the path of your car as you drive down a quiet neighborhood street. to avoid hitting the child that runs to re

KengaRu [80]

Since the acceleration of car is uniform so the distance traveled by car while brakes are applied is given by

$d = \frac{v_f + v_i}{2}*t$

given that

$v_f = 9 m/s$

$v_i = 15 m/s$

$t = 1.20 s$

now plug in all data in above formula

$d = \frac{15 + 9}{2} * 1.2$

$d = 14.4 m$

so car will cover 14.4 m distance while it apply brakes

5 0

3 years ago