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kvasek [131]
3 years ago
12

A 65 N boy sits on a sled weighing 52 N on a horizontal surface. The coefficient of friction between the sled and the snow is 0.

012. What is the magnitude of the frictional force?
Physics
1 answer:
pogonyaev3 years ago
3 0

Answer:

1.40 N

Explanation:

The magnitude of the frictional force is given by:

F=\mu N

where

\mu is the coefficient of friction

N is the magnitude of the normal reaction

The coefficient of friction for this problem is \mu=0.012. The magnitude of the normal reaction is equal to the combined weight of the boy and the sled, because the surface is horizontal, so

N=65 N+52 N=117 N

Therefore, the frictional force is

F=\mu N=(0.012)(117 N)=1.40 N

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A roadrunner at rest suddenly spots a rattlesnake slithering directly away at a constant speed of 0.75 m/s. At the moment the sn
Shalnov [3]

Answer:

The roadrunner will take approximately 5.285 seconds to catch up to the rattlesnake.

Explanation:

From the statement we notice that:

1) Rattlesnake moves a constant speed (v_{S} = 0.75\,\frac{m}{s}), whereas the roadrunner accelerates uniformly from rest. (v_{o, R} = 0\,\frac{m}{s}, a = 1\,\frac{m}{s^{2}})

2) Initial distance between the roadrunner and rattlesnake is 10 meters. (x_{o, R} = 0\,m, x_{o,S} = 10\,m)

3) The roadrunner catches up to the snake at the end. (x_{S} = x_{R})

Now we construct kinematic expression for each animal:

Rattlesnake

x_{S} = x_{o,S}+v_{S}\cdot t

Where:

x_{o, S} - Initial position of the rattlesnake, measured in meters.

x_{S} - Final position of the rattlesnake, measured in meters.

v_{S} - Speed of the rattlesnake, measured in meters per second.

t - Time, measured in seconds.

Roadrunner

x_{R} = x_{o,R} +v_{o,R}\cdot t +\frac{1}{2}\cdot a\cdot t^{2}

Where:

x_{o, R} - Initial position of the roadrunner, measured in meters.

x_{R} - Final position of the roadrunner, measured in meters.

v_{o,R} - Initial speed of the roadrunner, measured in meters per second.

a - Acceleration of the roadrunner, measured in meters per square second.

t - Time, measured in seconds.

By eliminating the final positions of both creatures, we get the resulting quadratic function:

x_{o,S}+v_{S}\cdot t = x_{o,R}+v_{o,R}\cdot t +\frac{1}{2}\cdot a \cdot t^{2}

\frac{1}{2}\cdot a \cdot t^{2} + (v_{o,R}-v_{S})\cdot t + (x_{o,R}-x_{o,S}) = 0

If we know that a = 1\,\frac{m}{s^{2}}, v_{o, R} = 0\,\frac{m}{s}, v_{S} = 0.75\,\frac{m}{s}, x_{o, R} = 0\,m and x_{o,S} = 10\,m, the resulting expression is:

0.5\cdot t^{2}-0.75\cdot t -10=0

We can find its root via Quadratic Formula:

t_{1,2} = \frac{-(-0.75)\pm \sqrt{(-0.75)^{2}-4\cdot (0.5)\cdot (-10)}}{2\cdot (0.5)}

t_{1,2} = \frac{3}{4}\pm \frac{\sqrt{329}}{4}

Roots are t_{1} \approx 5.285\,s and t_{2}\approx -3.785\,s, respectively. Both are valid mathematically, but only the first one is valid physically. Hence, the roadrunner will take approximately 5.285 seconds to catch up to the rattlesnake.

6 0
3 years ago
What are the 2 main categories of boat hull designs and how does each one function? What are the positives and negatives of each
defon

Answer:

The two main categories of boat hull designs are;

  • Displacement Hull
  • Planning Hull

Explanation:

<u>Displacement Hull</u>

This type of boat hull is designed to displace certain amount of water as it moves. This displacement enable it to insert its body into the water and continue to displace water from its was as it moves. The weight of water displaced is usually equal to the weight of the boat.

Displacement Hull and Speed

Because of the need to displace water from its path to enable it insert itself into the water body for movement, the speed is usually slow compared to planning hull boats.

Displacement Hull Types:

  • Round bottomed hull boat: Their hulls are made to have a round bottom in order to displace water and move smoothly through it. It can move quietly at low speed. How ever, they require complex stabilizer to control them from banking.
  • Multi hull boat: This type of hull design has a large and long beam that make it to be very stable on the water body. They usually have ends pointed downwards for proper insertion and displacement. However, they don't turn easily on small space due to their large beam requirement.

<u>Planning Hull</u>

Planning hull boats are designed to slide very fasly on the water surface with very little or no insertion. They require boat engines that operates at a very high revolution per minute(rpm).

When at rest, that is at zero speed, they behave like displacement hull boats but only a small amount of water is displaced a they are usually lighter.

Planning hull boats can operate in three modes:

  • Displacement mode: This mode is used when planning hull boats move at extremely slow speed. At this mode, they push water side ways as they move.
  • Planning mode: This mode is activated as the speed of the boat increases to enable it glide on the surface of the water.
  • Plowing mode: This mode is reach when the bow of the boat is trusted up and suspended as it slides through the surface of the water at a very high speed

Planning Hull and Speed

The speed of planning hull boats is very high when compared to displacement hull boats. This high speed of operation is powered by high rpm engines to enable it slide on the surface of the water.

Planning Hull Types/Merit and Demerit

  • Flat Bottom Hull: Their hull is flat bottom shaped and has a draft that supports its suspension on water on a stable manner. Suitable for stable water. However, it moves haphazardly on shaky water.
  • Deep Vee Hull: It has a V-shape hull that points towards the water body. Its V-shape makes it glide through rough water surfaces more smoothly than the flat bottom hull. However, it requires more power to operate and easily banks during sharp turning.
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A similarity between radio waves and microwaves is that both are used for _____.
Cloud [144]

Answer:

(B) Sending Messages

Explanation:

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Radio Waves and Microwaves have longer wavelengths and lower frequencies. Longer wavelengths than an x-ray which is in the electromagnetic spectrum and lower frequencies than gamma rays, which are also in the electromagnetic spectrum. They are also both electromagnetic radiation.

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Explanation:

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