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Wittaler [7]
3 years ago
12

A roller coaster is stationary at the top of a ramp.

Physics
1 answer:
Serjik [45]3 years ago
6 0

Answer:

A

Explanation:

The roller coaster is stationary so the kinetic energy would be zero, but it is at the top of ramp so the potential energy would be high as its gravitational  so it would have to be A

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A long copper rod of diameter 2.0 cm is initially at a uniform temperature of 100°C. It is now exposed to an air stream at 20°C
Lisa [10]

Answer:

t = 4.0 min

Explanation:

given data:

diameter of rod = 2 cm

T_1 = 100 degree celcius

Air stream temperature =  20 degree celcius

heat transfer coefficient = 200 W/m2. K

WE KNOW THAT

copper thermal conductivity = k = 401 W/m °C

copper specific heat Cp = 385 J/kg.°C

density of copper = 8933 kg/m3

charateristic length is given as Lc

Lc = \frac{V}{A_s}

Lc = \frac{\frac{\pi D^2}{4} L}{\pi DL}

Lc = \frac{D}{4}

Lc = \frac{0.02}{6} = 0.005 m

Biot number is given as Bi = \frac{hLc}{k}

Bi = \frac{200*0.005}{401}

Bi = 0.0025

As Bi is greater than 0.1 therefore lumped system analysis is applicable

so we have

\frac{T(t) - T_∞}{Ti - T_∞} = e^{-bt} ............1

where b is given as

b = \frac{ hA}{\rho Cp V}

b = \frac{ h}{\rho Cp Lc}

b = \frac{200}{8933*385*0.005}

b = 0.01163 s^{-1}

putting value in equation 1

\frac{25-20}{100-20} = e^{-0.01163t}

solving for t we get

t = 4.0 min

6 0
3 years ago
A baseball player throws a baseball with a velocity of 13 m/s north. It is caught by a second player seven seconds later. How fa
guajiro [1.7K]

Answer:

A. 91 meters north

Explanation:

Take +y to be north.

Given:

v₀ = 13 m/s

a = 0 m/s²

t = 7 s

Find: Δy

Δy = v₀ t + ½ at²

Δy = (13 m/s) (7 s) + ½ (0 m/s²) (7 s)²

Δy = 91 m

The displacement is 91 m north.

7 0
3 years ago
the police department determined that the force required to drag a 130 N(29 lb) car tire across the pavement at a constant veloc
ki77a [65]
The force of friction is given by:
f = μR, where μ is the friction coefficient and R is the reaction force, which will be equal to the weight.
100 = μ x 130
μ = 0.77
4 0
3 years ago
A 900-kg giraffe runs across a field at a rate of 50 km/hr. What is the magnitude of its momentum? 18 km/hr
Yuri [45]
The correct answer is the one with 45000 kg*km/hr.
the formula is p = m*v 
 900 *50/hr  giving u 45000 
I know this is the correct answer because i have already turned it in and got a 100%.  
7 0
3 years ago
Read 2 more answers
The Reynolds number, rho VD/mu, is a very important parameter in fluid mechanics. Verify that the Reynolds number is dimensionle
Agata [3.3K]

Answer:

Re = 1 10⁴

Explanation:

Reynolds number is

         Re = ρ v D /μ

The units of each term are

       ρ = [kg / m³]

       v = [m / s]

      D = [m]

      μ = [Pa s]

The pressure

      Pa = [N / m²] = [Kg m / s²] 1 / [m²] = [kg / m s²]

      μ = [Pa s] = [kg / m s²] [s] = [kg / m s]

We substitute the units in the equation

      Re = [kg / m³] [m / s] [m] / [kg / m s]

      Re = [kg / m s] / [m s / kg]

      RE = [ ]

Reynolds number is a scalar

Let's evaluate for the given point

Where the data for methane are:

viscosity       μ = 11.2 10⁻⁶ Pa s

the density  ρ = 0.656 kg / m³

       D = 2 in (2.54 10⁻² m / 1 in) = 5.08 10⁻² m

       Re = 0.656 4 2 5.08 10⁻² /11.2 10⁻⁶

       Re = 1.19 10⁴

4 0
3 years ago
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