Physical Science
Review of Ch 10-
forces (and velocity/acceleration)
Rom. Num. I and II
1. Write the equation for each:
a. Speed = distance/time
b. Acceleration= (speed#2- Speed #1)/ time
2. Give an example of speed= __3km/s__
; Give an example of velocity= ___3km/s North___
3. Solve this Speed problem:
a. John runs 40 miles in 20 minutes. What is his speed? (be sure to include the
units)
2 miles/min.
4. Solve this Acceleration problem:
a. John starts out the race running
10km/hr and finishes the race going 8 km/hr.
It takes him .5 hrs to run
the race. What was his acceleration?
(include units) -4km/hr2
b. Was the answer positive or
negative? ___neg._ Why? because he is slowing down
c. Did you remember the “2” at the
end of the units? yes!
5. Define:
a. Force - a push or a pull in a certain direction
b. Friction -
the force that two surfaces exert on each other
as they rub together. Friction always
pulls in the opposite direction of motion
c. Free fall - when the only force acting on an object is gravity
d. Gravity - the pull between any two objects
6. What are the units used to
measure force? Newtons
7. Who were the units named after? Sir Isaac Newton
8. Here is a picture of a boy on a
bike. Label at least 4 forces that act on the boy or his bike. Use arrows to show the direction the force is
pushing/pulling.
(I cannot use the arrows on the site)
Force#1 - the boy/bike has Fluid friction as the wind blows against him
Force #2 - The boy has gravity pulling down on him and the bike
Force #3 - Air pressure is pushing on him from all directions
Force #4 - This body has fluid in the cells which is pushing outward in all directions (which keeps him from imploding!)
Force #5 - the boys feet are exerting force on the pedals, which is overcoming the other forces and allowing forward motion.
9. What is Net Force? The total amount of all forces acting on an object.
10. Explain the difference between
balanced forces and unbalanced forces.
Use an example in your explanation. In a situation where there is a balance of forces an object will not move, such as when a block sits on an inclined ramp. If the ramp's incline becomes steep enough, the pull of gravity will become stronger than the static friction and the block will start to move. This is because the forces have become unbalanced.
11. List the four types of friction and
include a simple drawing with each
a. ___Static friction____(a brick on a ramp)
b. ___Fluid Friction_____(water running by a rock in a river)
c. ___Rollling Friction____(a wheel rolling)
d. ___Sliding Friction____(ice skating)
12. True or False (fix the false statements)
a. __T__ Gravity acts on all objects
b. __F__ distance does not affect
gravity
c. __F__ the bigger the mass the
smaller the gravitational force
d. __F__ 9.8 m/s2 is the pull of
gravity on the planets in our solar system
e. __T__ weight is a measurement of
the earth’s gravity pulling an object’s mass.
f. __T__ mass is the same regardless
of the planet you are on.
g. __F__ heavier objects fall faster
in Free Fall
13. What does it take for an object
to reach terminal velocity? The force of the air resistance on the object must equal the force of gravity's pull on the object (it's weight).
14. What does terminal velocity mean? It means that the object will not go any faster. It will not accelerate any more.
15. Air resistance is an example of
what type of friction? Fluid Friction
16. Does air resistance increase the
faster you go?___Yes___ why? Because the faster you go the more space you travel through and the more air molecules you will run into on your journey.
17. We looked at many examples of
forces. Choose 1 example from the list
below and explain how this example illustrates something that we have learned
about forces. Use complete sentences and
go for a “level 3” answer.
a. Skydiving
b. Interwoven phonebook pages
c. Bobsled racing
d. Shoe tread
answers may vary
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