NAME______DATE______CLASS PERIOD___

MUSCULAR SYSTEM DISCOVERY ACTIVITY

Activity 1: Examining How a Popper Works

Obtain a popper and figure out how it works.

1.Once you have the toy working properly, write a brief description of the workings and the resulting motion of this toy

Activity 2: Modeling How Bending Your Legs Helps You Jump

Jump 3 times, each time trying to jump a little bit higher.

2.Can you jump keeping your legs completely straight? Does the amount of bending of your legs have any relation to how far up you can jump? Describe your results.

3.Is energy stored in your legs when bent? How do you know?

Activity 3: Modeling How the Stretch of Tendons andMuscles Helps You Jump

Obtain a rubber bandand use it to launch a small wad of paper straight up in the air. DO NOT SHOOT IT AT ANYONE! Experiment with the function of this equipment. If you have trouble shooting a small piece of paper, you might just try shooting the rubber band straight up into the air.

4.Once you have the system working properly, write a description of the workings and the motion of this rubber band/paper apparatus.

5. What variables of this apparatus change the height to which the paper flies? Describe the differences in height for each variable.

6. How is the action of the rubber band similar to the action of tendons and muscles?

Activity 4: The BIG Idea:Stress and Strain

Stress and Strain

When a force is applied to any object, it changes its shape (even if you cannot see it).

The force applied to an object is called stress
(Stress = force/area).
So you are stressing your muscles and bones when you apply forces to them.
The change of shape of an object relative to its original size when it is acted upon by a force, or stressed, is called strain
(Strain = L/L0).

If an object is elastic, once the stress is relieved, the object will return to its original shape. If an object, under stress and has been deformed beyond its elastic limit then it will NOT return to its original shape after the stress is relieved.

The stresses, or forces, that are exerted on your muscles and bones can damage them and cause you aches and pains or dysfunction. When muscles pull too hard, they can over stretch themselves and the attached tendon, and they can compress the joint to the point of damage. The elasticity of your bones and muscles changes with age, exercise, etc.

Activity 5: Applying the BIG Idea to Something Familiar

Obtain a gummy bear from your teacher.Remember that % Strain = L/L0 x 100

7.Measure the original length of your gummy bear. ______cm

Apply a stress (with your hands) to compress the gummybear

(a)What is the change in length? ______cm
Calculatethe resulting strain. (Show Work)

(b)Is energy stored in the compressed gummy bear?
How do you know?

(c)Is it elastic? How do you know?

Obtain a gummy worm from your teacher. Remember that % Strain = L/L0 x 100

8.Measure the original length of your gummy worm. ______cm

Apply a force, this time to stretch the gummy worm a small amount.

(a)What is the change in length? ______cm
Calculatethe resulting strain. (Show work)

(b)Is energy stored in the stretched gummy? How do you know?

(c)Is it elastic? How do you know?

Tendons can stretch to 8% of their original length and muscle fibers only 3%.
Use this information to answer the following questions.

9.Imagine the gummy worm is a tendon. Considering its original length, calculate the maximum length it can be stretched to without causing damage. Show your work.

10.Imagine the gummy worm is a muscle. Considering its original length, calculate the maximum length it can be stretched to without causing damage. Show your work.

11.Considering what you have learned, why are muscles strains more
common than strains of tendons?