Forces in everyday life

Friction

• Is the force which opposes movement

Motion Friction

Astronaut Kelly Nyberg

What is causing the difference in the 2 images?

What force(s) are acting on the seedlings?

Gravity

• Is the force of attraction between objects that have mass.– Mass is a measure of the amount of “stuff” in an

object. All objects have mass.

Emergence of a Seedling

https://www.youtube.com/watch?v=SHaJhc-o--Q

Geotropism• “geo”-earth• “tropism”- movement or response to external

stimuli.• Geotropism or Gravitropism is the growth of

the parts of plants with respect to the force of gravity

Geotropism cont..

• The force of gravity cause the roots of the plant to grow towards the Earth’s core where gravity is strongest and the stem or leaves to grow up towards the sun.

• The roots are growing in a positive direction, while the stem or leaves are growing in the negative direction with respect to the force of gravity.

• Draw root, seed, and stem• Draw a line to show the soil level• Top half: stem grows up, opposite to the force

of gravity (negative force)• Bottom half: roots grow downwards towards

Earth’s center, where gravity is strongest (positive force)

What is Geotropism?A plants response to the effects of the earth.

Positive geotropic

Negative geotropic

What is Positive Geotropism?

Roots bending and growing downwards, towards the center of the Earth

Positive geotropic

Negative geotropic

What is Negative Geotropism?

Shoots bending and growing upwards, or away, from the surface.

Which of the following seedling images shows a root that is positively stimulated by gravity?

1. The school garden club placed several potted plants outside in various positions to investigate root and stem growth. Which of the plants above

correctly shows the response of these plants?F. Plant AG. Plant BH. Plant CJ. Plant D

Questions

• What would happen if there was no gravity?• How the plants grow (roots and stem)?• What if there was no sunlight?• Is gravity doing work on plants? How do we

know?

Video of matches

• http://www.youtube.com/watch?v=qrp7V0Q5qYQ

What happened to the matches AND what caused it?

Celery Video

• What happened to the celery AND what caused it?

Turgor Pressure: is the main pressure of the cell contents against the cell wall in plant cells. It can also help with the movement of a plant

This force gives the plant rigidity, and may help to keep it erect. Turgor can result in the bursting of a cell.

Turgor Pressure

Lacks turgor pressure

PLANT CELLS: Vacuole• The plant cell vacuole

also regulates turgor pressure in the cell.

• Water collects in cell vacuoles, pressing outward against the cell wall.

• Without sufficient water, turgor pressure drops and the plant wilts (droops)

Water entering the cell

Pressure applied from vacuoles

Wilting in Plants

It occurs as the plant’s cells lose turgor pressure and shrink.

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If a plant loses too much water, causes the stem and leaves to bend downward.

Wilting in Plants

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Plants lose water from tiny pores in their leaves, in a process called transpiration.

These tiny pores are called stomata.

Turgor Pressure

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ANIMATION

• http://www.kscience.co.uk/animations/turgor.htm

What happens to plants when they receive too much water?

https://www.youtube.com/watch?v=zytz31XrogE

Turgor Pressure: Examine the two plants below:

1.Write down 2 similarities and difference between the two plants?2.What causes the right plant to wilt?3.What do you think is the organelle that is responsible for the wilting of plants? Why?

The picture shows a turgor pressure demonstration using celery. Place the pictures of the celery in order of least amount of pressure to the greatest amount of pressure.

A) Q, R, S, TB) S, R, Q, TC) Q, R, T, SD) S, T, Q, R

Complete a magazine cover

Daily Turgor

Your cover must contain a title, picture, and article titlesBelow the cover you must provide an explanation of your cover and its contents

Articles within

(4)

Example: ways to increase your vacuole size

An explanation for each article.

EX: increasing your vacuole size will increase the turgor pressure of the plant cell.