FORCES - push and pull: The weight
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TRY without hint first.
lab forces
PART1: A force is a vector. It is a push or a pull. It has a magnitude and a direction
1)
Fill the blank:
This man is pulling the block to the right.
In that case the force is a pull in a specific direction (@right in that case).
A force is measured in Newton.
For example, the person is pulling
with a force of 100N@right
1 newton = 0.22 pounds so
100N = _____________
Understand that a force not only has a magnitude (100 here) but also a unit(Newton) and a direction (@right). In 10th grade you will learn that a force is called a vector.
A force has a magnitude (how much), a unit (of what) and a direction (which way).
Read: Pushes and pulls are forces. Whenever you are pushing or pulling, lifting or bending, twisting or tearing, stretching or squeezing, we are exerting a force.
Go on: http://www.pbs.org/wgbh/buildingbig/lab/forces.html
and find out about different examples of force.
check that page too:
http://www.usoe.k12.ut.us/CURR/Science/sciber00/8th/forces/sciber/forcmot.htm
2) Observe this image:
There are 4 forces acting on the plane.
For each force, describe its direction and its origin. source:
http://www.grc.nasa.gov/WWW/K-12/airplane/forces.html
3) Observe the image:
A) What are the 2 forces acting on the block?
B)complete, we write: F = 10N@right and f = ____ @ _____
C) 10N = _____ lbs (hint: with 1 N = 0.22 pounds)
4) SAme as 3)
What are the 2 forces acting on the skydiver (call it W and f for short)?
What are the directions ?
Suppose the person weight is 200 pounds and suppose he is going down at a constant
speed. (that means that the weight is balanced by the air resistance or W = f)
convert 200 pounds to newton. 200lbs = ________N
W = ___N @ ______ and f = ____N @ _____
5) A Physics book is placed on a horizontal table.
It is not moving/ (the 1st image)
2 forces balance each other. The weight Fw and the normal force Fn.
A)Discuss the origin of these forces
B) suppose the book weight's is 2 pounds. convert to newton. 2 lbs= _____N.
Fn = _____ N @ ______ ; Fw = _______N @ ___________
C) If the book is placed on on inclined plane, describe the forces that can act
on the book : A) if the surface is really slippery (2nd image) or rough.
6) (take-home quiz ?)
The electric force, the force of gravity and the magnetic forces all act at distance.
observe the pictures and answer questions:
(use wikipedia or other Internet source or a book!)
A) picture 1. You might know that like charges (like proton/proton or electron/electron) repel and opposite charges attract (like proton and electron).
Why electrons stay around the nucleus? If like charges repell why the protons stay inside the nucleus without repelling each other and without flying off?
B) picture2. The North pole of a magnet attracts the South pole. Like poles repel : North repels South and South repels North. On Earth, the North pole of the needle of a compass points toward the geographic North . (North seeking pole). Every thing happens like inside the EArth was a huge bar magnet.
The South pole of this imaginary bar magnet is the geographic North or the geographic south? How scientists explain the magnetic field of the EArth (explain this bar magnet)?
How can you explain the boreal aurora ? The magnetic field of the Earth shields us from
the solar wind. Why is the solar wind dangerous ?
C) picture3. Sir Isaac Newton found out about the force of gravity/ He was trying to understand why the planets orbit the Sun and why the moons orbit the planets,
without flying away. he also discovered that it is again the force of gravity that
explains projectile motion. If you throw an object (projectile) horizontally, it will follow a parabola before hitting the ground.
It is said that Newton unified motion in the heaven and motion on Earth. Why ?
(see movie below gravity or no gravity )
7) Draw all the forces acting on the skier
PART II: the weight, gravity
1) Read: Weight is the force due to the attraction of gravity.
The force of gravity, called weight, is pulling you downward,
toward the center ot the Earth.
weight (N) = mass (kg) x g , g depends on the planet and it also
depends on the distance from the object to the center of the planet. For EArth,
at sea level, it is about 9.8 m/s2. The unit tells you what physical quantity is g
m/s2 = m/s/s is the unit for ____________. (see last unit) .
It means that an object falling on EArth, if we neglect air resistance, will speed up toward the ground at a rate of 9.8 m/s2. Every second, the object will go 9.8m/s
faster.
2) Complete the sentences
The force due to gravity on an object is the __________, unit is the _________ (N)
The quantity of matter in an object is the _________ , unit is the _________(kg)
The amount of space an object occupies is the ____________, unit is __________
3) Complete the table (take g=9.8m/s/s)
1N = 0.22 lbs
4) Find your weight on other planets.
Remember: 1 N = 0.22 pounds use:
weight in newton x 0.22 = weight in pounds ; weight in newton = mass in kg x g (m/s2)
5) John's mass is 65kg on earth. What his metric (a) mass and (b) weight on Mars, where g= 3.72m/s/s. m=____kg and W = _________N
On Mars, a falling object will speed up by ______ m/s every second.
6) Find out your mass in Kg. (use the bathroom balance) _________kg.
What are your metric mass and weight on Jupiter where g = 25.9 m/s/s ?
m = _________kg and W = ________N. Convert your weight to pounds ______ lbs.
7) Find the mass of a 11,500N automobile. m = _____kg. convert to pounds ______ lbs.
8) A student use a balance scaled in newton to find the weight of 1kg and then 2 kg.
He finds that 1 kg = _______ N, 2kg = ________ N, 3 kg = __________ N ... 10kg = _________N
THe mass is proportional to the pull due to gravity (weight) and the constant pf proportionality is_______
9) See the picture below.
Find the gravity on the moon: g = ______ Your weight on Earth is divided by _____
but your mass is the ______________.
PART III going further
1) gravity or no gravity ?
what Einstein's theory of general relativity has to say?Maybe you don't need gravity to explain the motion of the EArth around the Sun. Maybe the curvature of time and space explain that motion. watch that movie (from NOVA)
2) Have you heard of dark matter? nothing to do with Star War. When studying, for example,
our own galaxy (the milky way) , and other part of the universe, the scientists found out something really strange.
They computed the total mass that they can see (all the stars and visible objects) and they
came to a certain amount of mass too small to explain the speed of these objects around the
center of the galaxy. Indeed, according to the laws of Physics the force of gravity (produced by the total amount of mass) must be large enough to prevent the objects (like stars) to fly off their galaxy. You will learn that in more details in 11th grade)
They were missing 80% of the total mass ! We don't know what a large part of the universe is made of ! This unknown mass is called the dark matter. Some say, it must be really small particles called wiggs and some say they must be very large object like neutron stars called macho.
Check on the Internet what wimps and machos stand for.
3) here another evidence for dark matter: the Bullet Cluster
4) watch this movie about dark matter
5) dark matter can be mapped because of its effect it has on the matter around it. Scientists used a method called gravitational lensing to map dark matter in 3D. These movies explain how.
without sound
6) Some scientists were able to map in 3D this dark matter.(using the method gravitational lensing)
8) What about dark energy ?
Scientists at Berkeley College in cAlifornia proved Einstein was right. The Universe is expanding as shown by Hubble, but it is expanding faster and faster. It is accelerating. It was predicated by Einstein who rejected his own prediction calling it his biggest blunder. This acceleration can be only explained by some kind of unknown force pulling the universe outward. It is called the dark energy.
watch that movie
9) black holes
10) worm hole: time machine ?
gravity can slow down the time. One consequence of Einstein's general relativity is the
existence of worm holes that could allow us to move from one part of the universe to the other.
we can't go faster than the speed of light but we could use worm homes
learn more:
1)
Fill the blank:This man is pulling the block to the right.
In that case the force is a pull in a specific direction (@right in that case).
A force is measured in Newton.
For example, the person is pulling
with a force of 100N@right
1 newton = 0.22 pounds so
100N = _____________
Understand that a force not only has a magnitude (100 here) but also a unit(Newton) and a direction (@right). In 10th grade you will learn that a force is called a vector.
A force has a magnitude (how much), a unit (of what) and a direction (which way).
Read: Pushes and pulls are forces. Whenever you are pushing or pulling, lifting or bending, twisting or tearing, stretching or squeezing, we are exerting a force.
Go on: http://www.pbs.org/wgbh/buildingbig/lab/forces.html
and find out about different examples of force.
check that page too:
http://www.usoe.k12.ut.us/CURR/Science/sciber00/8th/forces/sciber/forcmot.htm
2) Observe this image:
There are 4 forces acting on the plane.
For each force, describe its direction and its origin. source:
http://www.grc.nasa.gov/WWW/K-12/airplane/forces.html
3) Observe the image:
A) What are the 2 forces acting on the block?
B)complete, we write: F = 10N@right and f = ____ @ _____
C) 10N = _____ lbs (hint: with 1 N = 0.22 pounds)
4) SAme as 3)
What are the 2 forces acting on the skydiver (call it W and f for short)?
What are the directions ?
Suppose the person weight is 200 pounds and suppose he is going down at a constant
speed. (that means that the weight is balanced by the air resistance or W = f)
convert 200 pounds to newton. 200lbs = ________N
W = ___N @ ______ and f = ____N @ _____
5) A Physics book is placed on a horizontal table.
It is not moving/ (the 1st image)
2 forces balance each other. The weight Fw and the normal force Fn.
A)Discuss the origin of these forces
B) suppose the book weight's is 2 pounds. convert to newton. 2 lbs= _____N.
Fn = _____ N @ ______ ; Fw = _______N @ ___________
C) If the book is placed on on inclined plane, describe the forces that can act
on the book : A) if the surface is really slippery (2nd image) or rough.
6) (take-home quiz ?)
The electric force, the force of gravity and the magnetic forces all act at distance.
observe the pictures and answer questions:
(use wikipedia or other Internet source or a book!)
A) picture 1. You might know that like charges (like proton/proton or electron/electron) repel and opposite charges attract (like proton and electron).
Why electrons stay around the nucleus? If like charges repell why the protons stay inside the nucleus without repelling each other and without flying off?
B) picture2. The North pole of a magnet attracts the South pole. Like poles repel : North repels South and South repels North. On Earth, the North pole of the needle of a compass points toward the geographic North . (North seeking pole). Every thing happens like inside the EArth was a huge bar magnet.
The South pole of this imaginary bar magnet is the geographic North or the geographic south? How scientists explain the magnetic field of the EArth (explain this bar magnet)?
How can you explain the boreal aurora ? The magnetic field of the Earth shields us from
the solar wind. Why is the solar wind dangerous ?
C) picture3. Sir Isaac Newton found out about the force of gravity/ He was trying to understand why the planets orbit the Sun and why the moons orbit the planets,
without flying away. he also discovered that it is again the force of gravity that
explains projectile motion. If you throw an object (projectile) horizontally, it will follow a parabola before hitting the ground.
It is said that Newton unified motion in the heaven and motion on Earth. Why ?
(see movie below gravity or no gravity )
7) Draw all the forces acting on the skier
PART II: the weight, gravity
1) Read: Weight is the force due to the attraction of gravity.
The force of gravity, called weight, is pulling you downward,
toward the center ot the Earth.
weight (N) = mass (kg) x g , g depends on the planet and it also
depends on the distance from the object to the center of the planet. For EArth,
at sea level, it is about 9.8 m/s2. The unit tells you what physical quantity is g
m/s2 = m/s/s is the unit for ____________. (see last unit) .
It means that an object falling on EArth, if we neglect air resistance, will speed up toward the ground at a rate of 9.8 m/s2. Every second, the object will go 9.8m/s
faster.
2) Complete the sentences
The force due to gravity on an object is the __________, unit is the _________ (N)
The quantity of matter in an object is the _________ , unit is the _________(kg)
The amount of space an object occupies is the ____________, unit is __________
3) Complete the table (take g=9.8m/s/s)
1N = 0.22 lbs
| Object | Mass | Weight in newtons | weight in pounds |
| melon | 1 kg | ______ N | ____________ lbs |
| apple | ___________ | 1 N | _______ lbs |
| physics book | find out, use a balance | _________ N | __________lbs |
| uncle harry | 60kg | __________ N | __________ lbs |
| automobile | 1,150 kg | __________ N | __________ lbs |
4) Find your weight on other planets.
Remember: 1 N = 0.22 pounds use:
weight in newton x 0.22 = weight in pounds ; weight in newton = mass in kg x g (m/s2)
| Planets | m = Mass (Kg) | acceleration due to gravity (m/s2) | Weight (N) | Weight (lbs) |
| Earth | 60kg | 10 (about) | 600 | 132 |
| Moon | 60kg | _________ | 99.6 | _________ |
| Mercury | _________ | _________ | 226.8 | _________ |
| Venus | _________ | _________ | 544.2 N | _________ |
| Mars | _________ | _________ | 226.2 N | _________ |
| Jupiter | _________ | _________ | 1416.0 N | _________ |
| Saturn | _________ | _________ | 549.6 N | _________ |
| Uranus | _________ | _________ | 533.4 N | _________ |
| Neptune | _________ | _________ | 672.0 N | _________ |
| Pluto | _________ | _________ | 35.4 N | _________ |
5) John's mass is 65kg on earth. What his metric (a) mass and (b) weight on Mars, where g= 3.72m/s/s. m=____kg and W = _________N
On Mars, a falling object will speed up by ______ m/s every second.
6) Find out your mass in Kg. (use the bathroom balance) _________kg.
What are your metric mass and weight on Jupiter where g = 25.9 m/s/s ?
m = _________kg and W = ________N. Convert your weight to pounds ______ lbs.
7) Find the mass of a 11,500N automobile. m = _____kg. convert to pounds ______ lbs.
8) A student use a balance scaled in newton to find the weight of 1kg and then 2 kg.
He finds that 1 kg = _______ N, 2kg = ________ N, 3 kg = __________ N ... 10kg = _________N
THe mass is proportional to the pull due to gravity (weight) and the constant pf proportionality is_______
9) See the picture below.
Find the gravity on the moon: g = ______ Your weight on Earth is divided by _____
but your mass is the ______________.
PART III going further
1) gravity or no gravity ?
what Einstein's theory of general relativity has to say?Maybe you don't need gravity to explain the motion of the EArth around the Sun. Maybe the curvature of time and space explain that motion. watch that movie (from NOVA)
2) Have you heard of dark matter? nothing to do with Star War. When studying, for example,
our own galaxy (the milky way) , and other part of the universe, the scientists found out something really strange.
They computed the total mass that they can see (all the stars and visible objects) and they
came to a certain amount of mass too small to explain the speed of these objects around the
center of the galaxy. Indeed, according to the laws of Physics the force of gravity (produced by the total amount of mass) must be large enough to prevent the objects (like stars) to fly off their galaxy. You will learn that in more details in 11th grade)
They were missing 80% of the total mass ! We don't know what a large part of the universe is made of ! This unknown mass is called the dark matter. Some say, it must be really small particles called wiggs and some say they must be very large object like neutron stars called macho.
Check on the Internet what wimps and machos stand for.
3) here another evidence for dark matter: the Bullet Cluster
4) watch this movie about dark matter
5) dark matter can be mapped because of its effect it has on the matter around it. Scientists used a method called gravitational lensing to map dark matter in 3D. These movies explain how.
without sound
6) Some scientists were able to map in 3D this dark matter.(using the method gravitational lensing)
8) What about dark energy ?
Scientists at Berkeley College in cAlifornia proved Einstein was right. The Universe is expanding as shown by Hubble, but it is expanding faster and faster. It is accelerating. It was predicated by Einstein who rejected his own prediction calling it his biggest blunder. This acceleration can be only explained by some kind of unknown force pulling the universe outward. It is called the dark energy.
watch that movie
9) black holes
10) worm hole: time machine ?
gravity can slow down the time. One consequence of Einstein's general relativity is the
existence of worm holes that could allow us to move from one part of the universe to the other.
we can't go faster than the speed of light but we could use worm homes
learn more: