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2 years ago

8

Tyler stands at rest on a skateboard. He has a mass of 120 kg. His friend (m = 60 kg) jumps into his arms at a speed of 2 m/s. I

f Tyler catches his friend, how fast will they move on the skateboard?

1 answer:

Andrews [41]2 years ago

5 0

Momentum question. This is an inelastic collision, so

m1v1+m2v2=Vf(m1+m2)
Vf=(m1v1+m2v2)/(m1+m2)=[(120kg)(0m/s)+(60kg)(2m/s)] / (120kg+60kg)
Vf=120kg m/s / 180kg
Vf=0.67m/s

0.67m/s

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A solid plate, with a thickness of 15 cm and a thermal conductivity of 80 W/m·K, is being cooled at the upper surface by air. Th

Nezavi [6.7K]

To solve this problem we will use the two principles that are visible according to the phenomena described in the problem: Heat transfer by conductivity and Heat transfer by convection.

This thermal transfer will be equivalent and with it we can find the value asked.

<em>Note: We will assume that the temperature value at the plate surface is: 60 ° C (For the given value of 650 50)</em>

For Thermal Transfer by Conduction

$Q_{cn} = -kA \frac{\Delta T}{\Delta x}$

$Q_{cn} = -kA \frac{T_1-T_2}{L}$

Where,

k = Thermal conductivity

A = Cross-sectional Area

$T_2$ = Temperature of the bottom surface

$T_1$ = Temperature of the top surface

L = Length

Replacing we have that

$Q_{cn} = -(80W\cdot K)(A)\frac{50\°C-60\°C}{15cm\frac{1m}{100cm}}$

$Q_{cn} = 5333.33A$

For Thermal Transfer by Convection

$Q_{cv} = hA(T_1-T_{\infty})$

Where,

h = Convection heat transfer coefficient

$T_{\infty}$ = Surrounding temperature

A = Surface Area

Replacing we have that

$Q_{cv} = hA(50\°C-10\°C)$

$Q_{cv} = 40hA$

Since the rate of heat transfer by convection is equal to that given by conduction we have to:

$Q_{cn}=Q_{cv}$

$5333.33A = 40hA$

$h = 133.33W/m^2\cdot K$

It is stated that the typical values of forced convection of gases lies in the range of $(25-250)W/m^2\cdot K$ . The obtained value is reasonable for forced convection of air.

7 0

2 years ago

two people, each with a mass of 70 kg, are wearing inline skates and are holding opposite ends of a 15m rope. One person pulls f

Zina [86]

Answer:

7.75 s

Explanation:

Newton's second law:

∑F = ma

35 N = (70 kg) a

a = 0.5 m/s²

Given v₀ = 0 m/s and Δx = 15 m:

Δx = v₀ t + ½ at²

(15 m) = (0 m/s) t + ½ (0.5 m/s²) t²

t = 7.75 s

5 0

2 years ago

When a resistor with resistance R is connected to a 1.50-V flashlight battery, the resistor consumes 0.0625 W of electrical powe

ch4aika [34]

Answer:

4.41 W

Explanation:

P = IV, V = IR

P = V² / R

Given that P = 0.0625 when V = 1.50:

0.0625 = (1.50)² / R

R = 36

So the resistor is 36Ω.

When the voltage is 12.6, the power consumption is:

P = (12.6)² / 36

P = 4.41

So the power consumption is 4.41 W.

5 0

2 years ago

A crate is lifted vertically 1.5 m and then held at rest. The crate has weight 100 N (i.e., it is reese (enr647) – HS OnRamps 04

icang [17]

Answer:

W = 0 J

Explanation:

It is given that,

Weight of the crate, W = 100 N

Distance moved by the crate, d = 1.5 m

Let W is the work done to hold the crate 1.5 m above the ground in this way. It is given by the product of force and the displacement. Its formula is given by :

$W=F\times d\times cos\theta$

Here, $\theta=90^{\circ}$ as it is lifted vertically

$W=100\ N\times 1.5\ m\ cos(90)$

W = 0

So, the work done to hold the crate is 0. Hence, this is the required solution.

5 0

2 years ago

Read 2 more answers

Of the following systems, which contains the most heat?

densk [106]

Answer:d

Explanation:

Given systems are state of matter and do not contain any heat instead Heat is required to change Phase or raise the temperature of the particular system.

For example 600 kg of ice at $0^{\circ}C$

Heat Required to convert it to water at $0^{\circ}C$ is

$Q=m\times L$

Where L=latent heat of Fusion $=334 J/gm$

$Q=600\times 334\times 1000$

$Q=200.4 MJ$

8 0

2 years ago