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3 years ago

BRAINLIESTTT!! HELP ME!!!

Physics

1 answer:

likoan [24]3 years ago

6 0

The efficiency of the scissor is 200%.

<u>Explanation:</u>

Efficiency is defined as the ratio of output of any instrument or device or machine to the input supplied to it. So the greater the output the greater will be the efficiency of the device.

As here the work done by us on the system is said to be 10 J so this will be equal to the input work done on the system. And the work done by the system i.e., the scissor is 20 J, so this will be the output work.

So, the efficiency is the ratio of output to input as shown below.

Efficiency = $(\frac {20} {10} ) \times 100$ = 200

So, the efficiency of the scissor is 200%.

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3 years ago

Heat is transferred at a rate of 2 kW from a hot reservoir at 800 K to a cold reservoir at 300 K. Calculate the rate at which th

vekshin1

Answer:

0.00417 kW/K or 4.17 W/K

Second law is satisfied.

Explanation:

Parameters given:

Rate of heat transfer, Q = 2kW

Temperature of hot reservoir, Th = 800K

Temperature of cold reservoir, Tc = 300K

The rate of entropy change is given as:

ΔS = Q * [(1/Tc) - (1/Th)]

ΔS = 2 * (1/300 - 1/800)

ΔS = 2 * 0.002085

ΔS = 0.00417 kW/K or 4.17 W/K

Since ΔS is greater than 0, te the second law of thermodynamics is satisfied.

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3 years ago

a car was traveling at 30.0 m/s when a small child darted onto the road 60.0 m away. Reacting instantly the driver slams the bra

Galina-37 [17]

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3 years ago

To win the game, a placekicker must kick a football from a point 44 m (48.1184 yd) from the goal, and the ball must clear the cr

Ganezh [65]

Answer:

The distance by the ball clear the crossbar is 1.15 m

Explanation:

Given that,

Distance = 44 m

Speed = 24 m/s

Angle = 31°

Height = 3.05 m

We need to calculate the horizontal velocity

Using formula of horizontal velocity

$u_{x}=u\cos\theta$

Put the value into the formula

$u_{x}=24\cos(31)$

$u_{x}=20.5\ m/s$

We need to calculate the vertical velocity

Using formula of vertical velocity

$u_{y}=u\sin\theta$

Put the value into the formula

$u_{y}=24\sin(31)$

$u_{y}=12.3\ m/s$

We need to calculate the time

Using formula of time

$t=\dfrac{d}{u_{x}}$

Put the value into the formula

$t=\dfrac{44}{20.5}$

$t=2.1\ sec$

We need to calculate the vertical height

Using equation of motion

$h=u_{y}t+\dfrac{1}{2}at^2$

Put the value into the formula

$h=12.3\times2.1-\dfrac{1}{2}\times9.8\times(2.1)^2$

$h=4.2\ m$

We need to calculate the distance by the ball clear the crossbar

Using formula for vertical distance

$d=h-3.05$

Put the value of h

$d=4.2-3.05$

$d=1.15\ m$

Hence, The distance by the ball clear the crossbar is 1.15 m

7 0

3 years ago

An object has a weight of 9 n when it is in air and 7.2 n when it is submerged into water. what is the specific gravity of the o

White raven [17]

The specific gravity of the object’s material is 5.09.

<h3>To calculate the specific gravity of the object:</h3>

Weight difference = 9 - 7.2 = 1.8 N = Buoyant force of water

Buoyant Force in water(Fb) = density of water x g x volume of the body(Vb)

1.8 = 1000 x 9.81 x Vb

Vb = 1.8/9810 cubic meter

Now, in the air;

Weight of body = mg = 9 N

Mass of body,m = 9/9.81 Kg

So,

Density of body = m/ Vb

= 9/9.81 ÷ 1.8/9810

= 5094.44 kg per cubic meter

The specific gravity of body = density of body ÷ density of water

= 5094.44 ÷ 1000

= 5.09

Therefore, Specific gravity of body = 5.09

Learn more about Specific gravity here:

brainly.com/question/13258933

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1 year ago