Download Physics Phorce Practice ---------------------------------

Physics Phorce Practice ---------------------------------- finding a force that’s part of the NET force
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1. A rope hoists a 20. kg crate upwards with an upward acceleration of 4.0 m/s2
a. Draw a FBD(free body diagram) of the crate labeling the forces.
b. Determine the net force
c. What is the crate’s weight?
d. Determine the force of the rope on the crate (Tension)
2. The same crate is now lowered at a constant velocity
a. Draw a new FBD
b. What is the new tension in the rope?
3. The same crate is now lowered with a downward acceleration of 6.0 m/s2.
a. draw another FBD
b. What is the new net force ?
c. Write an equation for the net force base it on the fbd
d. solve for the new tension force:
Name______________________________
Friction
Review
1. What is the normal force?_____________________________________________________________
2. If a 10 Newton box is sitting on a horizontal floor, what's the normal force?_____________________
3. What is the normal force if a 10 kg box is on a horizontal floor?______________________________
4. Write the equation from the reference table that includes  .__________________________
5. What is  basically?_________________________________________________________________
6. What is the difference between static friction and kinetic?__________________________________
___________________________________________________________________________________
7. Which is always larger?______________________ (static friction or Kinetic)
8. Which surfaces are the most slippery (use table p.1)_________________
9. Which surfaces have the highest friction?______________________
10. Use the formula from #4 and the table above to find the maximum force of static friction for a 10 kg
copper block about to be slid across a horizontal steel floor:
11. If someone pushes the same block from #10 at that force, 52 N, and it slides determine the new force
of friction (kinetic)
11b. What would the block’s acceleration be? (use a = Fnet/m)
Don’t worry friction isn’t that rough!
1. A 22 kg crate is being slid along a floor a constant velocity of 2.5 m/s
with a horizontal force of 105 N.
a. draw a labeled free-body diagram of the box: Label Fg,, Fn (normal force),
Pull, Friction
b. What is the weight of the box?
The normal force(F n)?
c. The net force (Fnet)
d. Force of kinetic friction?
e. Determine the coefficient of kinetic friction.
2. A 150 kg box is accelerated horizontally along a floor with a horizontal force of 410 N. If the coefficient of
kinetic friction is 0.25,
a. draw a labeled free-body diagram of the box: Label Fg,, Fn (normal force), Pull, Friction
b. determine the acceleration of the crate.
3. Dr. Davenport tries to pull a 15.0 kg wooden box of student of the month pens with a force of 42.0 N across
horizontal wood floor.
a. Use Ff = FN and page 1 coefficients to show why the box won’t start to slide.
b. At what force will the box just start to silde?
c. If Dr. D pulls at that force (61.8 N), what will be the acceleration of the box?