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4 years ago

Which statement correctly defines power?

Physics

1 answer:

Anna007 [38]4 years ago

6 0

Answer:

$Power=V\, I$ which corresponds to the second option shown: "voltage times amperage"

Explanation:

The electric power is the work done to move a charge Q across a given difference of potential V per unit of time.

Since such electrical work is the product of the potential difference V times the charge that moves through that potential, and this work is to be calculated by the unit of time, we need to divide the product by time (t) which leads to the following final simple equation:

$Power=\frac{V\,Q}{t} =V\,\frac{Q}{t} = V\, I$

Notice that we replaced the quotient representing charge per unit of time (Q/t) by the actual current running through the circuit.

This corresponds to the second option shown in the question: "Voltage times amperage".

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A 62.6-kg skateboarder starts out with a speed of 2.18 m/s. He does 113 J of work on himself by pushing with his feet against th

n200080 [17]

Answer:

a. Wgra=786.09J

b. 1.28m

Explanation:

The change in the potential energy is the work done by the gravitational force.

For this problem you have to take into account that the total work done is given by the change in the kinetic energy

$W_{tot}=\Delta E_k=\frac{m}{2}(v_f^2-v_0^2)\\W_{tot}=\frac{62.6kg}{2}((6.55\frac{m}{s})^2-(2.18\frac{m}{s})^2)=1194.09J$

Furthermore the total work is the contribution of the work done by the skater, the gravitational force and the friction

$W_{tot}=W_{ska}+W_{fric}+W_{gra}$

(a) by separating Wfric you have

$W_{gra}=W_{tot}-W_{fric}-W_{ska}=1194.09J-295J-113J=786.09J$

(b) It is only necessary to use the expression for the work done by gravitational force

$W_{grav}=mgh\\h=\frac{W_{grav}}{mg}=\frac{786.09J}{(62.6kg)(9.8\frac{m}{s^2})}=1.28m$

HOPE THIS HELPS!!

6 0

3 years ago

10. Calculate A ramp is

inna [77]

Answer: 3.33

Explanation:

MA = De/Dr

MA = 5.0/1.5

MA= 3.33

5 0

4 years ago

HELP ME PLEASE

olga55 [171]

1) False

2) True

3) The distance is 17 m

4) The displacement is 2 m south

5) She did not give the direction as either left, or negative.

6) The average speed is 28 mph

7) The average velocity is 12 mph north

8) The average speed is 0.27 m/s

9) False

10) False

Explanation:

Speed is a scalar quantity which tells how fast an object is moving regardless of its direction, and it is calculated as:

$speed=\frac{d}{t}$

where d is the distance covered by the object and t is the time taken. Being a scalar quantity, speed consists only of a value and its units, so no direction needs to be specified.

Velocity is a vector quantity, defined as

$velocity = \frac{d}{t}$

where d is the displacement of the object (a vector connecting the initial position to the final position of motion) and t is the time taken. Being a vector, velocity has both a magnitude and a direction (the same direction as the displacement), so direction here should also be specified.

The distance travelled by the object is just the total length of the path taken, regardless of the direction of each part of the motion.

Here the object moves:

10 meters to the right

7 meters to the left

So, the distance travelled is

d = 10 + 7 = 17 m

The displacement is a vector connecting the initial position to the final position of motion, so we have to compare the starting position with the final position.

Taking x = 0 as initial position, and north as positive direction:

- The object moves 5 m north first (+5)

- The object moves 7 m south (-7)

So, the displacement is

d = +5 + (-7) = -2 m

which means 2 meters south.

As we said previously, displacement is a vector connecting the initial position to the final position of motion. Being a vector, it must have:

- A magnitude (the shortest distance between the initial and final position, in a straight line)

- A direction

Here Jenny reported only the magnitude (3 meters), but not the direction, so she forgot to include the direction of the displacement (which is to the left).

The average speed is given by

$speed=\frac{d}{t}$

where d is the distance and t is the time taken.

The distance is just the total length covered, so:

d = 5 + 2 = 7 miles

The time taken is

t = 1/4 h = 0.25 h

So, the average speed is

$speed=\frac{7}{0.25}=28 mph$

The average velocity is given by

$velocity=\frac{d}{t}$

where d is the displacement and t is the time taken.

The displacement is, taking north as positive direction:

d = +5 + (-2) = 3 miles (north)

The time taken is

t = 1/4 h = 0.25 h

So, the average velocity is

$velocity=\frac{3}{0.25}=12 mph$ (north)

We can calculate the average speed by adding the single measurements and dividing by the number of trials done:

$speed_{avg}=\frac{s_1+s_2+s_3}{3}$

where in this case, N = 3. For this experiment we have:

$s_1 = \frac{0.75 m}{2.5s}=0.30 m/s\\s_2 = \frac{0.75 m}{2.75 s}=0.27 m/s\\s_3=\frac{0.75 m}{2.98 s}=0.25 s$

So the average is

$speed_{avg}=\frac{0.30+0.27+0.25}{3}=0.27 m/s$

Data are said to be:

- Accurate, when the average value of the measurements is close to the actual value

- Precise, when the spread of the measurements done in the different trials is small

Therefore, the first part of the sentence "Data that is accurate, is data that is really close to the actual value" is correct, and the second part "data that is precise is data that is repeated over and over again" is not correct, since we may have several measurements but their spread may be large.

10)

As we said in part 9):

- Accuracy refers to how close the measured value is to the actual value

- Precision refers to the spread (or the uncertainty) on the measured value: the smaller it is, the better the precision

For instance, let's assume that the actual value of a certain variable is 3.0. If we get the following set of data:

2.4, 2.5, 2.4, 2.3

it is precise (the spread is small) but not accurate (since the average, 2.4, is far from the actual value)

while the following set:

3.1, 3.6, 2.4, 3.0

is accurate (the average is around 3.0, so close to the actual value), but not precise (the spread is very large).

Learn more about speed and velocity:

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#LearnwithBrainly

4 0

4 years ago

Evidence of a chemical change includes

NNADVOKAT [17]

Answer:1.- b. Change in color.

It's change in color because the other can happen by via a physical change.

2.- d. A metal is added to an acid and hydrogen gas is formed.

A chemical change results in change of an object chemical structure being disrupted or altered.

Explanation:

3 0

4 years ago

A satellite is orbiting the Earth in a circular orbit of radius r. Its frequency is independent of its height above the surface

Pie

Answer:

a. TRUE

Explanation:

When a satellite is launched to orbit around earth, it has to produce its own artificial gravity by performing rotations. The frequency of this rotation is given by the following formula:

f = √[ac/4πR²]

where,

f = frequency

ac = centripetal acceleration

R = Radius of the satellite

Therefore, it is clear from this formula that the frequency of rotation of the satellite is independent of its height above the surface of earth. So, the correct option is:

5 0

3 years ago