1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
jeka94
3 years ago
6

9. Consider the elbow to be flexed at 90 degrees with the forearm parallel to the ground and the upper arm perpendicular to the

ground. There is a 0.5 kg spherical ball in the hand. The person rotates her arm upward producing an initial angular acceleration of 10 rad/s2 . The elbow and wrist remain rigid. What are the muscle moments about the shoulder and elbow joints
Physics
1 answer:
mojhsa [17]3 years ago
3 0

Answer:

Moment about SHOULDER  ∑ τ = 3.17 N / m,

Moment respect to ELBOW   Στ= 2.80 N m

Explanation:

For this exercise we can use Newton's second law relationships for rotational motion

         ∑ τ = I α

   

The moment is requested on the elbow and shoulder at the initial instant, just when the movement begins.

They indicate the angular acceleration, for which we must look for the moments of inertia of the elements involved

The mass of the forearm with the included weight is approximately 2.3 kg, with a length of about 50cm

Moment about SHOULDER

          ∑ τ = I α

           I = I_forearm + I_sphere

the forearm can be approximated as a fixed bar at one end

            I_forearm = ⅓ m L²

the moment of inertia of the mass in the hand, let's approach as punctual

            I_mass = m L²

we substitute

           ∑ τ = (⅓ m L² + M L²) α

let's calculate

          ∑ τ = (⅓ 2.3 0.5² + 0.5 0.5²) 10

           ∑ τ = 3.17 N / m

Moment with respect to ELBOW

In this case, the arm exerts an upward force (muscle) that is about 3 cm from the elbow

         Στ = I α

         I = I_ forearm + I_mass

         I = ⅓ m (L-0.03)² + M (L-0.03)²

         

let's calculate

        i = ⅓ 2.3 0.47² + 0.5 0.47²

        I = 0.2798 Kg m²

        Στ = 0.2798 10

        Στ= 2.80 N m

You might be interested in
The lowest-pitch tone to resonate in a pipe of length L that is closed at one end and open at the other end is 200 Hz. Which one
ozzi

Answer:

e. 400 Hz

Explanation:

In closed organ pipe,  only odd harmonics of fundamental note is possible .

The fundamental frequency is 200 Hz . Then other overtones will be having following frequencies .

200 x 3 , 200 x 5 , 200 x 7 , 200 x 9 etc

600 Hz , 1000 Hz , 1400 Hz  , 1800 Hz .

Frequency not possible is 400 Hz .

7 0
3 years ago
On what principle does a bottle opener work
Vsevolod [243]

Answer:

Bottle opener works on a fulcrum.

Explanation:

A bottle opener is a second-class lever because the pivot point is at one end of the opener and the load is in the middle.

8 0
3 years ago
A wire is stretched just to its breaking point by a force F . A longer wire made of the same material has the same diameter. The
ICE Princess25 [194]

Answer: No

Explanation:

The force F required is equal to the Force exerted in stretching the first material since conditions are the same

8 0
2 years ago
Read 2 more answers
For a top player, a tennis ball may leave the racket on the serve with a speed of 55 m/s (about 120 mi/h). If the ball has a mas
inn [45]

Answer:

Yes is large enough

Explanation:

We need to apply the second Newton's Law to find the solution.

We know that,

F= ma

And we know as well that

a= \frac{v}{t}

Replacing the aceleration value in the equation force we have,

F= \frac{mv}{t}

Substituting our values we have,

F= \frac{(0.060)(55)}{4*10^{-3}}

F=825N

The weight of the person is then,

W = mg

W = (60)(9.8) = 558N

<em>We can conclude that force on the ball is large to lift the ball</em>

6 0
2 years ago
A soccer player is running upfield at 10m/s and comes to a stop in 3 seconds facing the same direction. What is his acceleration
Mekhanik [1.2K]
The players acceleration is 3.33 m/s/s

Acceleration= Velocity/Time

A =10/3
4 0
3 years ago
Read 2 more answers
Other questions:
  • In EXACTLY 13 words explain how global warming happens on Earth.
    15·1 answer
  • A 282 kg bumper car moving right at 3.50 m/s collides with a 155 kg bumper car moving 1.8 m/s left. Afterwards, the 282 kg car m
    9·1 answer
  • A rope of total mass m hnd length L is suspended vertically with an object of mass M suspended from the lower end. Find an expre
    15·1 answer
  • Which of the following is a temporary magnet made by placing a piece of iron inside a current-carrying coil of wire
    8·1 answer
  • Take the distance between the Earth and the Sun to be 149,500,000,000 m. Calculate the velocity of the Earth in its
    15·1 answer
  • Where does the heat come from that drives this convection current in the mantle
    13·1 answer
  • The forces of gravity between the earth and the moon causes
    10·1 answer
  • A bear, searching for food wanders 35.0 meters east then 20.0 meters north. Calculate the angle of the bear's displacement (w/re
    5·1 answer
  • What is the difference between a chemical change and a physical change? *
    6·1 answer
  • According to current scientific understanding, the idea that the milky way galaxy might be home to a civilization millions of ye
    9·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!