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melamori03 [73]

2 years ago

5

Which is not true of friction? A. Causes wear and tear of the surfaces B. Helps us to fall easily on roads C. Produces heat D. P

roduces light E. Stops bodies when they move over each other.

2 answers:

Ganezh [65]2 years ago

5 0

Answer:

B.

Hope this helps

Aleks04 [339]2 years ago

3 0

The answer is B

i need 20 works

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Determine the speed of a falling object 7.8 sec after it dropped.

butalik [34]

Answer:

76.4m/s

Explanation:

Given parameter:

Time taken = 7.8sec

Unknown:

Speed after it dropped = ?

Solution:

To solve this problem, we use one of the kinematics equation:

V = U + gt

V is the final speed

U is the initial speed = 0m/s

g is the acceleration due to gravity

t is the time taken

V = 0 + 9.8 x 7.8 = 76.4m/s

7 0

3 years ago

An ice skater of mass m = 60 kg coasts at a speed of v = 0.8 m/s past a pole. At the distance of closest approach, her center of

IrinaVladis [17]

Answer:

1.78 rad/s

1.70344 rad/s

Explanation:

v = Velocity = 0.8 m/s

m = Mass of person = 60 kg

$r_1$ = Distance between center of mass of person and pole = 0.45 m

$r_2$ = New distance between center of mass of person and pole = 0.46 m

I = Moment of inertia

Angular speed is given by

$\omega_1=\dfrac{v}{r_1}\\\Rightarrow \omega_1=\dfrac{0.8}{0.45}\\\Rightarrow \omega_1=1.78\ rad/s$

The angular speed is 1.78 rad/s

In this system the angular momentum is conserved

$L_1=L_2\\\Rightarrow I_1\omega_1=I_2\omega_2\\\Rightarrow mr_1^2\omega_1=mr_2^2\omega_2\\\Rightarrow \omega_2=\dfrac{r_1^2\omega_1}{r_2^2}\\\Rightarrow \omega_2=\dfrac{0.45^2\times 1.78}{0.46^2}\\\Rightarrow \omega_2=1.70344\ rad/s$

The new angular speed is 1.70344 rad/s

7 0

3 years ago

In nuclear reaction 5 kg of reactants give 2kg of products

dlinn [17]

Choice A is correct.======Kinetic energy equation: KE = (1/2)(m)(v²)This tells us that KE is directly proportional to mass and the square of velocity. In other words, the more mass and more velocity an object has, the more kinetic energy.If an object is sitting at the top of a ramp, there is no velocity and therefore no kinetic energy. Choices B and D are wrong.A golf ball has more mass than a ping-pong ball, so a ping-pong ball would have less kinetic energy than a golf ball rolling off the end of a ramp. Choice C is wrong.Choice A is correct.

6 0

3 years ago

A green light is submerged 2.70 m beneath the surface of a liquid with an index of refraction 1.31. What is the radius of the ci

Anettt [7]

Answer:

The radius is $r = 3.1905 \ m$

Explanation:

From the question we are told that

The distance beneath the liquid is $d = 2.70 \ m$

The refractive index of the liquid is $n_i = 1.31$

Now the critical value is mathematically represented as

$\theta = sin ^{-1} [\frac{1}{n_i} ]$

substituting values

$\theta = sin ^{-1} [\frac{1}{131} ]$

$\theta = 49.76^o$

Using SOHCAHTOA rule we have that

$tan \theta = \frac{ r}{d}$

=> $r = d * tan \theta$

substituting values

$r = 2.7 * tan (49.76)$

$r = 3.1905 \ m$

5 0

3 years ago

A radio has 100J of energy transferred by electricity. 20J are transferred by heating and 10J are transferred by sound. How many

seraphim [82]

Answer:

70 Joules

Explanation:

3 0

3 years ago