YR7 Forces
Year 7 forces in action Chapter 8

Key Concepts


  1. What forces can do
  2. Magnetic attraction
  3. Static Electricity
  4. Mass and Weight
  5. Effects of Friction
NAME:

Science Quest 7
TEXTBOOK
SCIENCE Quest 7 PRACTICALS / ACTIVITIES
SCIENCE Quest 7
HOMEWORK
OTHER ACTIVITIES/RESOURCES
Year 7 Pre-test Forces
please ensure your students type your teacher initials and class before their first name: It makes it easier to find results!
First name = GW 7D Sally
Last Name = Brown

http://www.classroomclipboard.com/490625/Test/4ED86D3BDC3044429EBE02CE355FB9FF
Access Code CHP8PT
1
8.1 On the Move – how objects respond to a force; the difference between contact and non-contact forces; net effect of multiple forces on an object.
Suggestions:
8.1 page 264 water drops
8.2 page 265 what can a force do?
Design a flic flak expt go here for how to design an experiment
Understanding & Inquiring
page 267 Q’s 1-10
Words to Learn
Contact Force, Non-contact Force, Gravity, Magnetic and Electrostatic Force, Drag, Buoyancy
2
8.2 A Magnetic Attraction – magnetic materials; direction and strength of magnetic fields around a magnet; how electromagnets can be made and used.
8.3 page 268 what does a magnet attract?
8.4 page 269 poles apart
8.5 page270 mapping the magnetic field

If time allows-
Demo- 8.6 making a compass
8.7 making an electromagnet
Understanding & Inquiring
page 272 Q’s 1-14

Research – Q 22 page 126
Words to Learn
Permanent Magnet, Alloys, Temporary Magnet, North and South Pole, Compass
Magnetic Field, Electromagnet

http://www.youtube.com/watch?v=nvyL5s6hLjk
3
8.3 All Charged Up – atomic structure; static electricity and how electrostatic charges are formed; conducting and insulating materials.
Possible activities
-picking up confetti(paper) with charged plastic ruler
-Van de Graaff generator

8.9 page 275 defying gravity
Understanding & Inquiring
page 276 Q’s 1-13

The affect of electrostatic charges
Words to Learn
Atom, Nucleus, Electron, Proton, Neutron, Positive and Negative Charge, Neutral, Static Electricity, Conductor, Insulator, Van de Graaff Generator
4
8.4 Scale and Measurement – difference between mass and weight; variation in gravitational field strength; effect of air resistance.
8.8 page 278 more than one force?
8.12 page 280 the landing time of a parachute
Understanding & Inquiring
page 280 Q’s 1-18
Words to Learn
Mass, Kilogram, Weight, Newtons, Gravity, Orbit, Scales, Beam Balance
5
8.5 Friction-Friend or Foe – effect of friction on static and moving objects.
8.13 page 283 measuring friction
Understanding & Inquiring
page 284-285 Q’s 1-14
Words to Learn
Friction, Traction, Rough, Smooth, Lubricant, Fluid, Streamlined

quizlet revision https://quizlet.com/class/1688872/





Forces
A force is defined as either a push or a pull. We can see the effect of a force on an object if the object is made to move. The movement includes making a dent in a stress ball or stretching a rubber band.

Sometimes an object can have many forces acting on it at the same time. A paper plane flying in the wind has the force of the throw and the force of the wind and the gravity acting on it all at the same time.

Forces can be divided into contact forces and non contact forces. Some examples of contact forces are - Hand throwing a ball, bat hitting a ball, tug of war, opening a door,. Or more generally - push, pull, friction,
Some examples of non contact forces are the forces exerted by a magnets, gravity, electrostatic force.

We need a way to represent forces when we draw a diagram. So we do this with arrows of different lengths. The head of the arrow points in the direction the force is being exerted.


What do magnets attract?

Aim: To find out if magnets attract everything
Hypothesis: The magnet will attracct metal objects
Method

you design the method - what do you need to control or keep the same in each test of material
1.Put the magnet 3 cm from the material and observe
2. Put the magnet less than 0.5 cm from the material and observe
3. complete the table
Results

MATERIAL TO BE TESTED
The magnet was < 0.5 cm from the material
the magnet was 3 cm from the material
IRON NAIL


IRON FILINGS


TALC


PLASTIC STRAW


ALUMINIUM FOIL
TOOTHPICK
PAPER CLIP


COPPER


spoon








Conclusion
Not all metals are attracted to the magnet. but everything with iron in it was attracted to the magnet.

Things that are magnetic
Are generally made from iron, nickel and steel. They can be permanent magnets or temporary magnets. In all cases the atoms in the magnets line up with their North pole all point in the same direction.

A magnet produces lines of force that we call a magnetic field. See the expt above.

A compass can be used to find the North pole of a magnet. The red arrow will point toward the North pole and away from the the south pole. This is the same as finding the the north pole on Earth. The earth has a magnetic field going around it just like a small magnet.

Electromagnets
http://www.youtube.com/watch?v=nvyL5s6hLjk
are magnets that can be switched on and off. THey work by wrapping lots of coper wire around a large piece of iron and then passing a current through the copper wire. This makes the atoms in the iron line up like a magnet but only while the electricity is running through the coper wire.

We use electromagnets in speakers, earphones, TVs and as special switches in cars and houses.



Electrostatics

This is a special type of force that uses the distribution of electrons on the surface of a substance.
For example , when we rubbed the plastic rods with wool we were rubbing off electrons from wool onto the rod. This made the rod have a negative charge.

We can rub electrons off the rod by using a different material and this will give the rod a positive charge.

When we rubbed the balloon against our woollen jumpers we were rubbing electrons from the jumper to the balloon. This made the balloon get a negative charge. When we brought the balloon close to the hair , paper or water the balloon attracted the positive parts of those things

Things that are both negative repel each other

Things that are negative will attract things that are positive.

Things that are both positive will repel each other.

We summarise this by saying like charges repel and unlike charges attract.

The rules for attraction and repelling are
Like charges repel (ie two positives will repel or two negatives will repel)
UNLIKE charged rods will attract. (ie positives attract negatives.

The Electron's role in electrostatics

When we charge a plastic ruler by rubbing it on wool we are rubbing electrons off the wool onto the ruler making the ruler a negative charge.

For example If the ruler and the wool both had an equal number of electrons (eg 10) after the rubbing the ruler might have 13 electrons and the wool would only have 7 electrons. Because the ruler has more electrons it is more negative ( electrons are negative)












Balloon Expt.
Balloons were attracted to the wool when rubbed by the wool. This shows that one of them was positive while the other was negative.

Friction
Friction is a force that occurs between 2 surfaces as they rub past each other. We can see this when we apply the brake on our bike. The friction between the rubber and the wheel rim slows us down.

Other examples of friction are
1. ice skates on a ice - here they move very well compared to ice skates on carpet.
2.earthquakes are the result of friction between large plates of land.
3. falling over and getting a carpet burn.
4. walking or running on wet grass compared to concrete

Revision p 294
and complete question 1 to 15.

Gravity and weight
Mass is the amount of matter that makes up a thing.
Weight is a force exerted by matter when gravity affects that matter. We can say that weight force is the result of multiplying mass times gravity (acceleration due to gravity)

On Earth your mass and weight can be considered the same. But scientifically we really should be talking about weight force and mass.

The gravity = 9.8 m/s/s and your mass is 50 kg then your weight force = 9.8 x 50
=490 Newtons on earth

On the moon an astronaut with a mass of 50kg would have a weight force of
50kg x 1.62 (m/s/s) = 81 Newtons on Moon

on Mars a mass of 50kg would have a weight force of 50kg x 3.7 m/s/s = 185 Newtons

on Saturn a mass of 50 kg would have a weight force of 50kg x 10.5 m/s/s = 525 Newtons

Skydiving forces
When the skydiver leaves the plane the force of gravity is greater than the force of air resistance. When the force of gravity is balanced ( equals) the force of air resistance the skydiver can't fall any faster. We say she has reached terminal velocity (speed). When she pulls the parachute air resistance is increased and this slows her down.