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3 years ago

14

If you were trying to cross a river with the shortest possible time, would you aim your boat slightly upstream, directly across

the river, or slightly downstream?

1 answer:

Katyanochek1 [597]3 years ago

7 0

I would say downstream since the stream can push your boat, then you would have momentum and would just have to row towards the land.

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A container in the shape of a cube 10.0 cm on each edge contains air (with equivalent molar mass 28.9 g/mol) at atmospheric pres

Vikentia [17]

Answer:

a) m = 1.174 grams

b) F_g = 0.01151 N

c) F_c = 1013 N

Explanation:

Given:

- The length of a cube L = 10.0 cm

- The molar mass of air M = 28.9 g/mol

- Pressure of air P = 101.3 KPa

- Temperature of air T = 300 K

- Universal Gas constant R = 8.314 J/kgK

Find:

(a) the mass of the gas

(b) the gravitational force exerted on it

(c) the force it exerts on each face of the cube

(d) Why does such a small sample exert such a great force? (6%)

Solution:

- Compute the volume of the cube:

V = L^3 = 0.1^3 = 0.001 m^3

- Use Ideal gas law equation and compute number of moles of air n:

P*V = n*R*T

n = P*V / R*T

n = 101.3*10^3 * 0.001 / 8.314*300

n = 0.04061 moles

- Compute the mass of the gas:

m = n*M

m = 0.04061*28.9

m = 1.174 grams

- The gravitational force exerted on the mass of gas is due to its weight:

F_g = m*g

F_g = 1.174*9.81*10^-3

F_g = 0.01151 N

- The force exerted on each face of cube is due its surface area:

F_c = P*A

F_c = (101.3*10^3)*(0.1)^2

F_c = 1013 N

- The molecules of a gas have high kinetic energy; hence, high momentum. When they collide with the walls they transfer momentum per unit time as force. Higher the velocity of the particles higher the momentum higher the force exerted.

4 0

3 years ago

To meet a U.S. Postal Service requirement, employees' footwear must have a coefficient of static friction of 0.5 or more on a sp

motikmotik

Answer:

0.79 s

Explanation:

We have to calculate the employee acceleration, in order to know the minimum time. According to Newton's second law:

$\sum F_x:f_{max}=ma_x\\\sum F_y:N-mg=0$

The frictional force is maximum since the employee has to apply a maximum force to spend the minimum time. In y axis the employee's acceleration is zero, so the net force is zero. Recall that $f_{max}=\mu N$

Now, we find the acceleration:

$\mu N=ma_x\\\mu mg=ma_x\\a_x=\mu g\\a_x=0.83(9.8\frac{m}{s^2})\\a_x=8.134\frac{m}{s^2}$

Finally, using an uniformly accelerated motion formula, we can calculate the minimum time. The employee starts at rest, thus his initial speed is zero:

$x=v_0t+\frac{1}{2}a_xt^2\\2x=a_xt^2\\t=\sqrt{\frac{2x}{a}}\\t=\sqrt{\frac{2(3.2m)}{8.134\frac{m}{s^2}}}\\t=0.79 s$

8 0

3 years ago

What is the value of work done on an object when a 70-newton force moves it 9.0 meters in the same direction as the force?

marta [7]

630 watts - 9 x 70 = 630

4 0

3 years ago

Read 2 more answers

If a light Ray is reflected off the shiny surface at 170 degrees at what angle did the light-ray first strike the surface

garri49 [273]

10 degrees would be your answer hope this helps!

4 0

3 years ago

Read 2 more answers

What is the kinetic energy of an object that has a mass of 12 kg and moves with a velocity of 10 m/s

WITCHER [35]

Answer:

600 J

Explanation:

The formula to find the kinetic energy of an object is $\frac{1}{2}mV^2$

m = mass in kg
V = velocity in m/s
KE is measured in Joules just as all other forms of energy.

Now, let's plug in the variables we're given and simplify.

$\frac{1}{2}(12)(10)^2$
$\frac{1}{2}(12)(100)$
$(6)(100)$
$(600)$

Thus, the answer is 600 Joules.

6 0

2 years ago

Read 2 more answers