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gladu [14]
3 years ago
15

A 74 kg firefighter slides, from rest, 4.9 m down a vertical pole. (a) If the firefighter holds onto the pole lightly, so that t

he frictional force of the pole on her is negligible, what is her speed just before reaching the ground floor?
Physics
1 answer:
In-s [12.5K]3 years ago
6 0

Answer:

Her speed is 9.8 meter per second

Explanation:

Newton's second law states that acceleration (a) is related with force (F) by:

\sum\overrightarrow{F}=m\overrightarrow{a} (1)

Here the only force acting on the firefighter is the weight F=mg so (1) is:

mg=ma

Solving for a:

a=g

Now with the acceleration we can use the Galileo's kinematic equation:

Vf^{2}=Vo^{2}+2a\varDelta x (2)

With Vf the final velocity, Vo the initial velocity and Δx the displacement, because the firefighter stars from rest Vo=0 so (2) is:

Vf^{2}=2a\varDelta x

Solving for Vf

Vf=\sqrt{2g\varDelta x}=\sqrt{2(9.81)(4.9)}

Vf=9.8\frac{m}{s}

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g100num [7]

Answer:pounds

Explanation:

7 0
3 years ago
Filiberto va a 90m/s en su carri, de repente se distrae por un par de segundos y su velocdad pasa a 40 m/s ¿cual fue su acelerac
svet-max [94.6K]

Answer:

Filiberto experimenta una deceleración de 2\,\frac{m}{s^{2}}.

Explanation:

(The problem was written in Spanish. Hence, explanation will be held in Spanish).

Asúmase que Filiberto se distrae por 2 segundos, puesto que un par equivale a dos, y que el vehículo experimenta un aceleración constante. La deceleración experimentada por el vehículo se deriva de la siguiente fórmula:

a = \frac{v-v_{o}}{\Delta t}

a = \frac{40\,\frac{m}{s}-90\,\frac{m}{s} }{2\,s}

a = -25\,\frac{m}{s^{2}}

Filiberto experimenta una deceleración de 2\,\frac{m}{s^{2}}.

7 0
3 years ago
A rectangular block of copper has sides of length 15 cm, 26 cm, and 43 cm. If the block is connected to a 5.0 V source across tw
nexus9112 [7]

Answer:

the case is the one  with the greatest current, L=15 cm ,   i = 2.19 10⁸  A

Explanation:

Ohm's law is

          V = i R

Resistance is

         R = ρ L / A

Where L is the length of the electrons pass and A the area perpendicular to the current

      i = V / R

      i = V (A / ρ L)

      i = V / ρ  (A / L)

We can calculate the relationship between the area and the length to know in which direction the maximum currents

Case 1

      L = 0.15 m

      A = 0.26 0.43 = 0.1118 m2

      A / L = 0.1118 / 0.15

      A / L = 0.7453 m

Case 2

        L = 0.26 m

        A = 0.15 0.43 = 0.0645 m2

        A / L = 0.248 m

Case 3

       L = 0.43 m

       A = 0.15 0.26 = 0.039 m2

        A / L = 0.0907 m

We can see that the case is the one  with the greatest current, L=15 cm

Let's calculate the current

     i = 5 / 1.7 10⁻⁸ (0.7453)

      i = 2.19 10⁸  A

3 0
3 years ago
A sphere of plastic of radius = .100 m is completely immersed in water. The density of the plastic is 600 kg/m3. Since the plast
tekilochka [14]

To solve this problem we need to use the proportional relationships between density, mass and volume, together with Newton's second law.

The force can be described as

F = ma \rightarrow mg

Where,

m = Mass

g = Gravitational acceleration

At the same time the Density can be defined as

\rho = \frac{m}{V} \rightarrow m = \rho V

Where,

m = mass

V = Volume

Replacing the value of the mass at the equation of Force we have,

F = \rho V g

Since the difference between the two forces gives us the total Force then we have to

F_T = F_w - F_p

Where

F_w = Force of the water

F_p= Force of plastic

Therefore with the values for this force we have,

F_T = \rho_w Vg - \rho_p Vg

F_T = Vg(\rho_w - \rho_p)

F_T = (\frac{4}{3} \pi r^3) g(\rho_w - \rho_p)

F_T = (\frac{4}{3} \pi (0.1)^3) (9.8)(1000 - 600)

F_T = 16.412 N

Therefore the tension in the thread is 16.412N

3 0
3 years ago
The pedals on a bicycle give a mechanical advantage by allowing you to turn the pedals a __________ distance to turn the _______
denpristay [2]
Short distance to turn the circumference of the wheels. Mechanical advantage is load/effort I think
6 0
3 years ago
Read 2 more answers
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