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1 year ago

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Danielle is doing some DIY. She uses a 1.2kW electric saw for 20 minutes and then a 1000W electric sander for half an hour. Whic

h job is the more expensive in terms of electricity used - sawing or sanding?

1 answer:

mixas84 [53]1 year ago

4 0

Answer:

1.2kw because it is kilowatt

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Two friends of different masses are on the playground. They are playing on the seesaw and are able to balance it even though the

Svetradugi [14.3K]

1) They are able to balance the torques due to gravity.

The torque is equal fo Force * lever arm.

The force downward is due to gravity, Force = mass*gravity.

Then the heavier student will produce a bigger force downgar and he/she shall shorten the lever arm of his/her side, by placing himself closer to the rotation axis, than the lighter student.

6 0

2 years ago

A frog leaps up from the ground and lands on a step 0.1 m above the ground 2 s later. We want to find the vertical velocity of t

zhuklara [117]

Answer:

<em>You would use the kinematic formula:</em>

$\Delta y=V_{0y}\times t-g\times t^2/2$

Explanation:

The upwards vertical motion is ruled by the equation:

$y=y_0+V_{0y}\times t-g\times t^2/2$

Where:

$y \text{ is the position at the time }t:y=0.1m$

$y_0\text{ is the initial position: }y_0=0$

$t=2s$

$g\text{ is the gravitational acceleration: }\approx 9.8m/s^2$

$V_{0y}\text{ is the initial vertical velocity}$

Naming Δy = y - y₀, the equation becomes:

$\Delta y=V_{0y}\times t-g\times t^2/2$

Then, you just need to substitute with Δy = 0.1m, t = 2s, and g = 9.8m/s², ans solve for the intital vertical velocity.

7 0

1 year ago

Read 2 more answers

A scuba diver has his lungs filled to half capacity (3 liters) when 10 m below the surface. If the diver holds his breath while

rjkz [21]

To solve this problem it is necessary to apply Boyle's law in which it is specified that

$P_1V_1 =P_2 V_2$

Where,

$P_1$ and $V_1$ are the initial pressure and volume values

$P_2$ and $V_2$ are the final pressure volume values

The final pressure here is the atmosphere, then

$P_2 = 101325 \approx 1*10^5Pa$

$h = 10m$

$\rho_w = 1000kg/m^3$

$V_1 = 3.0L$

Pressure at the water is given by,

$P_1 = P_2 -\rho gh$

$P_1 = 1*10^5 +1000*9.8*10 =198000Pa$

Using Boyle equation we have,

$V_2 = \frac{P_1V_1}{P_2}$

$V_2 = \frac{198000*3*10^5}{10^5}$

$V_2 = 5.9L$

Therefore the volume of the lungs at the surface is 5.9L

4 0

1 year ago

A champion athlete can produce one horsepower (746 W) for a short period of time. The number of 16-cm-high steps a 70-kg athlete

erastovalidia [21]

Answer:

407 steps

Explanation:

From the question,

P = mgh/t........... Equation 1

Where P = power, m = mass, g = acceleration due to gravity, h = height, t = time.

Make h the subject of the equation

h = Pt/mg............. Equation 2

Given: P = 746 W, t = 1 minute = 60 seconds, m = 70 kg.

Constant: g = 9.8 m/s²

Substitute into equation 2

h = 746(60)/(70×9.8)

h = 44760/686

h = 65.25 m

h = 6525 cm

number of steps = 6525/16

number of steps = 407 steps

6 0

1 year ago

A 63.0 kg astronaut is on a spacewalk when the tether line to the shuttle breaks. the astronaut is able to throw a spare 10.0 kg

Llana [10]

There are other forces at work here nevertheless we will imagine it is just a conservation of momentum exercise. Also the given mass of the astronaut is light astronaut.

The solution for this problem is using the formula: m1V1=m2V2 but we need to get V1:

V1= (m2/m1) V2

V1= (10/63) 12 = 1.9 m/s will be the final speed of the astronaut after throwing the tank.

6 0

1 year ago

Read 2 more answers