For which situation is the perpindicular force of an object greater than the parallel force on an inclined plane: the angle is less than 45 degrees, greater than 45 degrees, or equal to 45 degrees? Explain.

For which situation is the perpindicular force of an object less than the parallel force on an inclined plane: the angle is less than 45 degrees, greater than 45 degrees, or equal to 45 degrees? Explain.

For which situation is the perpindicular force of an object equal to the parallel force on an inclined plane: the angle is less than 45 degrees, greater than 45 degrees, or equal to 45 degrees? Explain.

When is the perpindicular force equal to the weight of the object? Explain.

When is the parallel force equal to the weight of the object? Explain.

What is the advantage of using an incline if you want to move something heavy to a higher level? Explain why this is so:

12. A 50-kg box rests on a 40 degree inclined plane. A rope is attached and is holding it in place. Find F parallel and F perpindicular and draw the picture with all of the forces. (F par = 315 N; F per = 375 N)

Determine the postive and negative forces:

Write the Net Force Equation:

What is the tension in the rope if the box is at rest? (T = 315 N)

If the rope pulls with an extra 20 Newtons, what is the box's acceleration? (a = .4 m/s^2)

If the box has a negative acceleration of .6 m/s^2, which means it is going down the incline, what must the tension in the rope be? (T = 285 N)

Explain how you can prove Galileo's experimental result that mass does not matter for objects traveling down an inclined plane: they all have the same acceleration.

An object is being held on an inclined plane with a rope that has a tension of 450 Newtons. Assuming no friction, find the perpindicular force if the object actually weighs 750 Newtons. (600 N)

What is the angle of the incline? (36.9 degrees)

13. (For Honors Physics) A 1200-kg truck is pulling three 100-kg stones as shown below:

Step Two: Determine positive/negative forces for each mass:

Step Three: Write the net force equation for each mass:

Step Four: Solve for acceleration:

If the force exerted by the truck is 2,800 Newtons, will it pull the blocks up, or will the blocks pull the truck back? Show by obtaining the acceleration. (a = -.093 m/s^2).

If the truck is pulling with a force of 2,940 Newtons, does that necessarily mean the system is not moving? Explain using the proper physics Law.

If the truck s pulling with a force of 5,940 Newtons, find all of the tensions. (T1 = 3540 N; T2 = 2360 N; T3 = 1180 N).

13. (For Basic Physics) A 1200-kg truck is pulling a 300-kg stone as shown below:

Step Two: Determine positive/negative forces for each mass:

Step Three: Write the net force equation for each mass:

The acceleration equation derived from the net force equations is:

If the truck is pulling with a force of 2,940 Newtons, does that necessarily mean the system is not moving? Explain using the proper physics Law.

If the truck s pulling with a force of 5,940 Newtons, find the tension in the rope. (T = 3540 N)

14. Why is it easier to keep an object moving across the floor as opposed to getting it started?

What is the difference between static friction and kinetic friction? Draw the graph that represents both:

A 200.0-kg wooden box rests on a level wooden floor. If a person pushes with a force of 980.0 N will the box move? Draw the net force diagram. µk = .50 and µs = .80. (no because 980 < 1568 N)

With what force must the person push to make the box move? (greater than 1568 N)

After the person gets the box to move, he pushes with a force of 600.0 N. Will the box accelerate (specify speed up or slow down) or move at a constant speed? (accelerate because 600 < 980 N)

What force must be applied to move the box at a constant speed? (980 N)

What happens to the crate if the applied force is 1000 N (specify speed up or slow down)? (accelerate because 1000 > 980 N)

15. There are five keys to frictional force. Answer the following questions, and for each answer, fill in the keys on the lecture sheet:

a. How does static friction change as you apply more force to an object at rest?

b. Once the object starts to move, what happens to the frictional force (also specify which type of force takes over).

c. If the applied force is less than the kinetic frictional force, is the object accelerating or moving at a constant speed?

d. If the applied force is equal to the kinetic frictional force, is the object accelerating or moving at a constant speed?

e. If the applied force is greater than the kinetic frictional force, is the object accelerating or moving at a constant speed?

Based on all of those answers, there are two main differences between static friction and kinetic friction: name them.

1.

2.

A 50-kg sled rests on a level snow covered ground. A person pulls a rope attached to the sled at an angle of 40 degrees. If µk = .20 and µs = .30, and the person pulls the rope with a force of 200 Newtons, find the acceleration of the sled. (a = 1.6 m/s^2)

16. Two masses are on inclined planes and are attached by a rope over a pulley system as pictured below:

Step One: Draw the net force diagram:

Step Two: Determine the positive and negative forces for each mass:

Step Three: Write the net force equation for each mass:

Step Four: Solve for a:

As mass one increases (and its incline angle stays the same), what must happen to the angle of the second incline if mass two stays the same in order to keep the system from accelerating? Defend your answer.

If mass one is 50-kg and the incline is 30 degrees,and mass two is 100-kg, what must the second incline's angle equal if the system is to stay at rest?

17. A 75-kg wood crate is sitting on a 35 degree incline made of steel. The only force trying to hold the crate in place is friction. The static coefficient of friction is .65, and the kinetic coefficient of friction is .40. Draw the net force diagram.

Step Two: Determine Positive/Negative Forces:

Step Three: Write the net force equation:

What inequality must be true so that the crate will not slide down the incline? (In other words must the parallel force and frictional force compare?)

Determine if the crate will stay or slide: (The answer is slide, but you must show why with the inequality above)

If a rope were attached to the crate, how much force would you need to pull with (assuming friction is still present), to keep the crate from sliding? Answer this question using logic, because you know friction is helping you hold the crate. (31 N).

Now redraw the net force diagram with the rope included. In this situation, the rope is trying to hold the crate in place, so the frictional force must be drawn in the correct direction (Remember to think about whether or not the friction is helping you or hindering you):

Step Two: Determine Positive/Negative Forces:

Step Three: Write the net force equation:

Using the net force equation, solve for T and show you get the same answer you got in level 6 using logic. (31 N).

Suppose you started to pull the crate up the incline: what would happen to the direction of friction and why?

Redraw that net force diagram:

Step Three: Write the net force equation:

What is the only difference between this net force equation and the previous net force equation?

What force must you use to pull the crate up the incline at a constant velocity? (Remember; the crate is moving now!) (663 N).

18. Given the picture below, draw the net force diagram. Mass one has friction, but mass two does not.

Step Two:

Step Three:

Step Four: