Download Unit 03: Work And Forces in Living Things

Unit 03: Work And Forces in Living Things
TAKE NOTES:
All things have forces acting upon them. Even weight is a force. Gravity is a force. Unbalanced forces
cause motion. These forces are observable in the everyday life of organisms. In plants the emergence
of seedlings relies on unbalanced forces to allow the seedling to push its way to through the soil.
These unbalanced forces are often a response to a stimulus. A stimulus is something causing a
reaction or response.
DRAW THE DIFFERENT TYPES OF TROPISMS. LABEL THE STIMULUS AS POSITIVE OR NEGATIVE. Tropism: the way a plant grows in response to a stimuli in the environment. Tropisms are usually named
for the stimulus involved and may be either positive (towards the stimulus) or negative (away from the
stimulus).
a. Phototropism: growth response to light The stimulus is light, therefore positive phototropism is up,
towards the sunlight. Negative phototropism would be down.
-Plants bend towards light
a. Geotropism: growth response to gravity The stimulus is gravity, therefore positive geotropism is
down (towards gravity). Negative geotropism would be up.
-plant roots grow down with gravity, shoots (stems) grow up against gravity out of the soil.
a. Thigmotropism: growth response to touch . The stimulus is touch, therefore positive thigmotropism
is up. Negative thigmotropism is down.
-vines grow up around trees, venus flytrap closes when leaves are touched
a. Hydrotropism: is the growth response of a plant to water. The stimulus is water, therefore positive
hydrotropism is down, negative hydrotropism is up.
TAKE NOTES, AND DRAW A PICTURE OF TURGOR PRESSURE
Turgor Pressure - Force in the form of pressure allows herbaceous (a plant with leaves) stemmed plants
to stand erect. This turgor pressure also keeps vegetables crisp. Plants need water to maintain turgor
pressure, which helps to keep them erect. The leaves of this plant are droopy because of a lack of
water. Turgor Pressure is a force per unit area exerted outward on a plant cell wall by the water
contained in the cell vacuole. Remember the cell vacoule in a plant is where it stores water.
DRAW EACH OF THE 6 SIMPLE MACHINES
SIMPLE MACHINES: There are 6 types of simple machines:
1.
2.
3.
4.
5.
6.
A pulley is a simple machine that uses grooved wheels and a rope to raise, lower or move a load.
A lever is a stiff bar that rests on a support called a fulcrum (midpoint) which lifts/moves loads. (seesaw)
A wedge is an object with at least one slanting side ending in a sharp edge, which cuts material apart. (ax handle)
A wheel with a rod, called an axle, through its center lifts or moves loads.
An inclined plane is a slanting surface connecting a lower level to a higher level. (a ramp)
A screw is an inclined plane wrapped around a pole which holds things together or lifts materials.
TAKE NOTES:
Equation: WORK (J) =FORCE (N) x DISTANCE (m)
When a force is applied to an object and the object moves, work is being done. In the physical sense, work
is equal to the force multiplied by the distance. Work occurs when a force is used to move an object
over a distance. Force is measured in Newtons (N), distance is measured in meters (m), and work is a
calculated unit called Joules (J). Because most forces in living systems are small, it is difficult to
measure the amount of work done. When something doesn't move, no work is being done.
DRAW AND TAKE NOTES ON THIS PARAGRAPH:
A book at rest on a table top has no motion. There are two forces acting upon the book. One force, the
Earth's gravitational pull, exerts a downward force. The second force, the push of the table on the
book, pushes upward. Since these two forces are of equal magnitude and in opposite directions, they
balance each other. The book is said to be at equilibrium. There is no unbalanced force acting upon
the book and thus, the book maintains its state of motion, which is no motion. When all the forces
acting upon an object balance each other, the object will be at equilibrium. It will not change its state of
motion.
What is an unbalanced force? Newton's First Law of Motion declares that a force is not needed to keep
an object in motion. Slide a book across a table and watch it slide to a rest position. The book in
motion on the desk does not come to a rest position because of the absence of a force; rather it is the
presence of a force. That force being the force of friction, which brings the book to a resting position.
In the absence of a force of friction, the book would continue in motion with the same speed and
direction forever. A force is not required to keep a moving book in motion. In actuality, it is a force
(friction) which brings the book to rest.