What is the efficiency of the machine in Figure 7.2 if the weight of the box is 200 N and required 98 N of effort Force?

2. If you want 0. 250 a (250 milliamps) to flow around a circuit with a resistance of 400 ohms, what voltage do you need?

grigory [225]

Answer:

0.000625 V

Explanation:

The formula linking current , resistance and voltage is :

V = I/R

Voltage = Current / Resistance

Now we substitute values given in question :

Voltage = 0.250 / 400

Voltage (V) = 0.000625

Our final answer is 0.000625 V

Hope this helped and have a good day

5 0

1 year ago

Assume that the radius ????r of a sphere is expanding at a rate of 70 cm/min.70 cm/min. The volume of a sphere is ????=43???????

rodikova [14]

Answer:

the rate of change in volume with time is 280πr² cm³/min

Explanation:

Data provided in the question:

Radius of the sphere as 'r'

$\frac{d\textup{r}}{\textup{dt}}$ = 70 cm/min

Volume of the sphere, V = $\frac{\textup{4}}{\textup{3}}\pi r^3$

Surface area of the sphere as 4πr²

Now,

Rate of change in volume with time, $\frac{d\textup{V}}{\textup{dt}}$

= $\frac{d(\frac{\textup{4}}{\textup{3}}\pi r^3)}{dt}$

= $3\times\frac{\textup{4}}{\textup{3}}\pi r^2}\times\frac{dr}{dt}$

Substituting the value of $\frac{dr}{dt}$

= $3\times\frac{\textup{4}}{\textup{3}}\pi r^2}\times70$

= 280πr² cm³/min

Hence, the rate of change in volume with time is 280πr² cm³/min

4 0

2 years ago

A glass of water at 20°C or a glass of water at 80°C explain

KiRa [710]

Answer:

1. A glass of water at 80°C because the more heat it will recieve, the more temperature increases. Heat is a sort of energy so the more it is heated, the more energy the water will recieve. So in comparison to 20°C, 80°C has more energy in it because it has a higher temperature.

2. An aluminium can at 30°C because the more heat it will recieve, the more temperature increases. Heat is a sort of energy so the more it is heated, the more energy the aluminium will recieve. So in comparison to 20°C, 30°C has more energy in it because it has a higher temperature.

Brainliest pweaseee if it is the correct answer! <3 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

6 0

2 years ago

HELP ASAP! GIVING BRAINLIEST!

Blababa [14]

Answer:

1. Emma standing on top of mountain

Since she is at the rest position and at some height from the ground so here energy is due to gravitational potential energy

So we have

gravitational potential energy

$U = mgH$

2. Emma jumping down from mountain top

Due to free fall Emma will start moving with some speed in downwards direction so here we have

$KE = \frac{1}{2}mv^2$

motion energy

3. tension in rope at Emma’s lowest position

Due to stretch in the rope here position come to the lowest end and speed comes to zero so whole energy is converted into elastic potential energy

$U = \frac{1}{2}kx^2$

elastic potential energy

4. Emma bouncing back

Due to bouncing back she will again have its kinetic energy with some speed upwards

$KE = \frac{1}{2}mv^2$

motion energy

8 0

2 years ago

Read 2 more answers

SOMEONE PLEASE HELP WITH MY PHYSICS!!!! PLEASE HELP ME!!! I WILL GIVE BRAINLIEST!!!

Lynna [10]

6 ... A

9 ... A

10 ... ok

12 ... A

23 ... ok

24 ... A

8 0

2 years ago