10. Different types of forces
Non- Contact Forces
Gravity
Magnetic Force
Electrical Force
Contact Forces
Friction
Tension (Pull)
Air Resistance
Applied Force (Push)
Spring Force (Twist)
http://www.physicsclassroom.com/class/newtlaws/u2l2b.cfm
11. Measuring force
• We can measure a force with a forcemeter
Forces are measured
in units called
NEWTONS.
15. Lesson Objectives
• Explain why some objects float and
some objects sink
• Investigate if materials will float
based on it’s density
• Measure the density of substances
16. Upthrust and Gravity
Gravity is the pull of the earth
on something
Upthrust is the push upwards of
a liquid on something.
17. Objects weigh less in water
because the water pushes the
object upwards. This force is
called ______________
When __________ and
___________ are equal, the
object will FLOAT.
UPTHRUST
UPTHRUST
GRAVITY
18. When gravity is bigger than
upthrust, the object will _____
If upthrust is bigger than
gravity, the object will move
_________, out of the water.
SINK
UPWARDS
22. Method
1. Record the weight of the object using scales
2. Record it’s volume using the eureka can
3. Work out the density
4. Does it float or sink?
24. density
• It is the ____________________of an object
• It is the density of an object that will determine whether or not
an object will _____________ or sink in _________________
• If an object is ____________ dense than water it will float
• If an object is ______________ dense than water it will sink
water, less, heaviness, float, more
26. Upthrust in action
This boat has gravity pushing it down, and the upthrust of
the water pushing up.
Because the forces are balanced, the ship floats.
Upthrust
Gravity
27. If the forces on an object are balanced:
•an object that is not moving stays still
•an object that is moving continues to move at the same speed
and in the same direction
If the forces on an object are unbalanced:
•An object that its not moving starts to move
•An object that is already moving changes speed or direction
Balanced & unbalanced forces
What is the resultant force?
28. We can show the forces acting on an object using a force
diagram. In a force diagram, each force is shown as a
force arrow.
Forces are measured in:
Newtons (N)
An arrow shows:
•The size of the force (the longer the arrow, the bigger the
force)
•The direction in which the force acts.
29.
30. Copy & complete
• A force can be a push or a pull. It is measured in .........................
• If the forces acting on an object are balanced then it is ................... or travels at a ..................... speed
• If the forces acting on an object are unbalanced, then it is either changing .......................... or
......................................
• Mark diagrams with arrows to show forces.
• Write the name of the force
• Label diagrams balanced or unbalanced
• If the forces are unbalanced, show the biggest force with the biggest arrow
Car braking
Missile just
launched
31. 10 N 10 N
If you link two forcemeters and pull equally hard from both
ends, the forces recorded on both will be the same.
balanced forces
When forces are balanced
The forces acting on the central hooks cancel each other out
– they are equal in magnitude and opposite in direction.
Because the forces are balanced the hooks do not move.
32. 11 N 10 N
What happens if the pull on one end is greater than the pull
on the other end?
unbalanced forces
movement
When forces are unbalanced
The forces acting on the hooks are no longer balanced.
Both hooks will start to move to the left – their speed will
change. This is called acceleration.
Unbalanced forces lead to a change in speed or direction.
36. Starter: What is friction?
• Friction is a force that is always in the
opposite direction to the moving object
• It happens when two surfaces rub together
• Whenever any two objects rub together
there is a force that makes them not glide
smoothly
• Friction is also able to take the energy of
moving objects and turn it into heat
38. 2.Why do you
think that?
OBJECTS WITH
SMOOTHER SURFACES
TRAVEL FASTER
_________________________
_________________________
________________
1.What do you think?
____________
____________
____________
____________
____________
____________
____________
____________
____________
____________
________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
4.Do you
still think
this?
5.How could you improve?
YE
S No
3.How could you prove this?
(Hypothe
sis)
(Evaluatio
n) (Predictio
n)
(Metho
d)
39. • Measure 1 metre on a plank of wood
• Slide a block of material down a plank of
wood
• Time how long it takes to go down
• Repeat using a different type of material
40. 1.Re-arrange these surfaces into order of slipperiness from
least slippery to most slippery.
Thick Carpet
Wet concrete
Dry concrete
Ice
Wet Grass
Wet Mud
2.Do the following people want to make as much friction as
possible or as little friction as possible?
a. An ice skater performing a routine
b. A driver, driving a car on a wet road
c. A mountain biker riding down a steep muddy hill
