1. Warm up 9/9-10
What is the formula and momentum for a cannonball with a mass of 30 kg traveling at a velocity at 40 m/s
south.

2. Word Bank Spiral Page 62
Gravity
Electromagnetic force
Weak Nuclear force
Strong Nuclear force

3. Forces part 2

4. As a review.....
A force is a push or pull, or any action that has the ability to change motion.

5. Inertia
Resistance of any physical object to any change (motion, speed, velocity, rest).
It is a tendency for an object to travel in a straight line at a constant velocity

6. Force=mass x acceleration
Calculating force
Calculating the force of an object we need its
Mass and acceleration
Force=mass x acceleration
F= m x a

7. Calculating Acceleration
acceleration = distance/time
time
like = mph/seconds

8. Gravity and Weight The force of gravity on an object is called weight.
Mass and weight are not the same thing!
(Mass = how much stuff)
(Weight = the force of gravity pulling on that stuff)

9. Weight
A 10-kilogram rock has a mass of 10 kilograms no matter where it is in the universe.
A 10-kilogram rock’s weight however, can vary greatly depending on where it is.

10. 2 rules for gravity....
Bigger objects have a stronger gravitational force
Closer objects have a stronger gravitational force

11. Terminal velocity
Terminal velocity = point you stop accelerating to earth as you fall down
Gravity accelerates you towards the earth but the air pushes you back up creating drag.
Terminal velocity= 54 meters/second

13. Stop

14. Friction is a force that opposes motion.
Many kinds of friction exist.

15. Amount of friction depends on 2 things:
1. Type of surface
2. Amount of force

16. Surface Matters! Friction depends on both of the surfaces in contact.
Just read: (When the hockey puck slides on ice,
a thin layer of water between the rubber
and the ice allows the puck to slide easily.)

17. More force = More friction
The greater the force squeezing two surfaces together, the greater the friction force.
Try it with your
hands

18. Types of friction forces
Friction is a force, measured in newtons just like any other force.
Static friction keeps
an object at rest
from moving.

19. Sliding friction is a force that resists the motion of an object moving across a surface.

20. Other types of friction

21. Useful friction – just read!
Friction is also important to anyone driving a car.
Grooved tire treads allow
space for water to be
channeled away from the
road-tire contact point,
allowing for more friction
in wet conditions.

22. Useful friction cont. (Just keep reading)
Shoes are designed to increase the friction between their soles and the ground.
Why do you think these shoes increase friction?
Players wearing cleats can apply greater force against the ground to help them move and to keep from slipping.

23. Not so useful friction…
Can you think of examples where friction is not so helpful?
When you…..
Skin your knee……. falling ☹
Hit a rock on your skateboard…. and fall ☹
Trip…… and fall ☹
Run into a glass door… and fall ☹
Trying to run over ice….. And fall ☹