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3 years ago

Which of the following are not clues that a chemical reaction has taken place?

Physics

2 answers:

Sladkaya [172]3 years ago

6 0

Im thinking a and d but if its just one answer im thinking mostly a

NNADVOKAT [17]3 years ago

4 0

D. Constant Temperature.
When a chemical reaction occurs there is almost always a change in temperature.<span />

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A tradesman sharpens a knife by pushing it with a constant force against the rim of a grindstone. The 30-cm-diameter stone is sp

Lorico [155]

Answer:

a. 0.21 rad/s2

b. 2.205 N

Explanation:

We convert from rpm to rad/s knowing that each revolution has 2π radians and each minute is 60 seconds

200 rpm = 200 * 2π / 60 = 21 rad/s

180 rpm = 180 * 2π / 60 = 18.85 rad/s

r = d/2 = 30cm / 2 = 15 cm = 0.15 m

a)So if the angular speed decreases steadily (at a constant rate) from 21 rad/s to 18.85 rad/s within 10s then the angular acceleration is

$\alpha = \frac{\Delta \omega}{\Delta t} = \frac{21 - 18.85}{10} = 0.21 rad/s^2$

b) Assume the grind stone is a solid disk, its moment of inertia is

$I = mR^2/2$

Where m = 28 kg is the disk mass and R = 0.15 m is the radius of the disk.

$I = 28*0.15^2/2 = 0.315 kgm^2$

So the friction torque is

$T_f = I\alpha = 0.315*0.21 = 0.06615 Nm$

The friction force is

$F_f = T_f/R = 0.06615 / 0.15 = 0.441 N$

Since the friction coefficient is 0.2, we can calculate the normal force that is used to press the knife against the stone

$N = F_f/\mu = 0.441/0.2 = 2.205 N$

7 0

3 years ago

Your teacher's SUV can go from rest to 25 m/s (roughly 55mph) in 10 seconds, The car's velocity changes at a uniform rate.

maw [93]

Heidhebd bdjdishrhr bdjjdhdhrhr heheheh hdudjdhhf hdjdhdhf

4 0

3 years ago

two bowling balls each have a mass of 8kg. if they are 2 m apart, what is the gravitational force between them?

Scilla [17]

Answer:

1 x 10^-9 N

Explanation:

F = Gm²/d² = 6.674e-11(8²)/2² = 1.06784e-9

4 0

3 years ago

Light rays bend as they pass from air into water at an angle (not 90 degrees). this is refraction. air water normal incident ray

xxTIMURxx [149]

When light ray pass from air into water, its speed and wavelength change only the frequency of the light doesn't change.

Light travels slower in a medium of higher refractive index. It bends because of this change in speed. The wavelength of light also changes in order to maintain the constant frequency.

7 0

3 years ago

the face of a cube towards A is brightly and shiny and the face towards V is full black.State with reason the adjustments that s

MariettaO [177]

Explanation:

increase the distance of cube from black and dull substance

5 0

3 years ago