# Forces on and in the Body

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## 40 Questions

### What happens to gravity when you let go of a book?

Gravity becomes an unbalanced force

### What are some significant effects of long-term weightlessness on the human body mentioned in the text?

Decreased production of red blood cells

### In the human body, what happens when objects are stationary according to the text?

The body is in a state of equilibrium

### How do most skeletal muscles operate according to the text?

By acting as levers in lever systems

### Which force is responsible for holding the particles in the nucleus of an atom together?

Strong Nuclear Force

### What is the medical effect of gravitational forces mentioned in the text?

Formation of varicose veins in the legs

### Which force is responsible for forces resulting from electric charge?

Electromagnetic Force

### What may happen to a person's bone mineral if they become weightless, such as in an orbiting satellite?

Loss of bone mineral

### According to Newton's 1st Law of Motion, what happens to an object in motion?

It remains in motion at constant velocity

Applied Forces

### How does Newton's 2nd Law relate force to mass and acceleration?

$\text{Force} = \text{mass} \times \text{acceleration}$

### What is the main idea behind Newton's 3rd Law of Motion?

Every force has an equal and opposite reaction force

### What is the main function of the muscular forces described in the text?

To cause blood circulation and lung air intake

### Which force is responsible for the formation of varicose veins in the legs as mentioned in the text?

Gravitational Force

### What is the medical impact on bone mineral when a person undergoes long-term bed rest according to the text?

Bone mineral decreases

### Which force gives materials their strength, their ability to bend, squeeze, stretch, or shatter?

Electromagnetic Force

### What is the impact on bone mineral when a person becomes weightless, such as in an orbiting satellite?

Bone mineral decreases

### Which force holds the particles in the nucleus of an atom together?

Strong Nuclear Force

### What causes the radioactive decay of nuclei according to the text?

Strong Nuclear Force

### Which force is very large compared to gravity and is responsible for forces resulting from electric charge?

Electromagnetic Force

### In a second-class lever, where is the point of resistance located?

Between the fulcrum and effort

### What is the role of muscle contraction in a bone-muscle lever system?

Provides effort at the insertion on the bone

### Which type of lever has the pivot located between the effort and the load?

First-class lever

123 FLE

### What does mechanical advantage refer to in lever systems designed for force?

Decreasing force required

### How is a second-class lever utilized in the human body?

When standing on tip-toe

### What determines the mechanical advantage of levers in general?

Effort arm divided by resistance arm

### Which lever type allows a given effort to move a heavier load than it otherwise could?

Second-class lever

400 Newton

400 m/sec²

### Which effect mentioned in the text is related to changes in internal hydrostatic pressure due to acceleration?

Changes in internal hydrostatic pressure

### What is the resonant frequency of an organ directly dependent on according to the text?

Mass and elastic forces acting on it

### In order for the spine to be in equilibrium when lifting a weight with a horizontal back, what must happen?

The torque due to the muscles must balance the torque due to the weights.

### Why does lifting a weight incorrectly, with the back horizontal, result in so many back injuries?

The muscles must exert a force of more than 1000 N to balance the torque.

### When lifting a weight against your body, why does it exert a smaller torque compared to lifting it with the back horizontal?

The weight is held closer to the body.

### What happens to the torque when you hold the weight closer to your body while lifting it?

The torque decreases.

### Why do muscles need to exert a large force when balancing torques due to weights on the spine?

To ensure no net force acts on the spine.

### What can be inferred about weightlifting with knees bent and back straight based on the text?

It exerts little torque on the spine.

### How does holding a weight closer to your body affect the torque it exerts according to the text?

'Closer' reduces the lever arm, hence decreases the torque.

## Study Notes

• A force is a push or pull acting on an object that changes its motion.
• Types of forces: contact forces (applied forces, friction) and field forces (gravity, electromagnetic force).
• Contact forces require physical contact between objects.
• Field forces act through empty space.
• Newton's Laws of Motion:
• 1st Law (Law of Inertia): an object will stay at rest or in motion at constant velocity unless acted upon by an unbalanced force.
• 2nd Law: force equals mass times acceleration.
• 3rd Law: for every action, there is an equal and opposite reaction.
• Four fundamental forces in nature:
• Gravitational Force: an attractive force that exists between all objects; weakest force.
• Electromagnetic Force: results from electric charge; very large compared to gravity.
• Strong Nuclear Force: holds particles in the nucleus of an atom; strongest force but only acts over a short distance.
• Weak Force: a form of electromagnetic force involved in radioactive decay.
• Forces in and on the body:
• Muscular forces cause blood circulation and lung function.
• Molecular forces exist in bone and calcium atoms.
• Electric forces exist in the body.
• Gravitational forces affect medical conditions like varicose veins and bone loss.
• Effects of gravity on the body and medical conditions.
• Lever Systems:
• Levers consist of a beam or rigid rod pivoted at a fixed hinge or fulcrum.
• Levers divide into three types based on the location of the fulcrum, load, and effort.
• In the human body, bones act as levers, joints as fulcrums, and muscle contractions provide effort.
• Mechanical advantage formula: MAlever = Effort (force) arm / Resistance (load) arm.
• Example: lifting a weight with the back horizontal exerts a larger torque and requires greater force from muscles compared to lifting the same weight while keeping back straight.

This quiz explores the concept of forces acting on objects and within the body. It covers different types of forces such as applied forces, friction, gravity, and electromagnetic forces.

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