NEWTON'S LAWS AND FORCES REVIEW (REISENER, 2017)
Directions: Write in complete sentences and show work for math calculations (LESSU).
General Review Questions
1) Define Force.
2) Define the following forces: Fnet, Fa, Fg, Ff, and Fn.
3) What are the units for force? Hint: There are 2 answers. One answer should be in terms of kg, m, and s.
Newton’s 1st Law
4) State Newton’s 1st Law. Give an example.
5) What is another name for this law?
6) Define Inertia.
7) How do mass and inertia relate?
8) Can an object be at rest if forces are acting upon it? Explain.
9) What are the two types of behavior an object might display if the net force is zero?
10) Can an object change direction if no net force acts upon it? Explain.
Newton’s 2nd Law
11) State Newton’s 2nd Law.
12) Rearrange the equation to solve for m and then for a.
m =
a =
13) According to a unit analysis of Newton's 2nd Law, 1 Newton is equal to 1 ______.
14) Sketch an example Atwood Machine showing M1 resting on a table, and M2 hanging off the end of the table. Assume that M1 = 5 kg, and M2 = 2 kg.
15) Using F=MA, solve for the acceleration of the system you sketched above.
16) Determine what will happen for the following situations.
a) If you double mass while keep acceleration constant, what happens to the force required?
b) If you want to cut the acceleration in half while keeping force constant, what must happen to mass?
17) If a 12 kg object is accelerated at 2.5 m/s2, what is the net force?
18) What is the mass of object that is accelerated at 5 m/s2 with a force of 75 N?
Weight
19) What force is also known as weight?
20) What equation helps us to find Fg?
21) What happens to mass and weight if you go to a different planet?
22) What is the weight of 7.2 kg book?
23) What is the mass of 1200N person?
Friction
24) Why does sliding friction exist?
25) What does friction always oppose?
26) What equation relates Ff and ?
27) Rearrange the above equation to find
µ =
FN =
28) What is µ?
29) What is the coefficient of friction dependent on?
30) If you increase the weight of an object, what happens to the:
a) Friction?
b) Coefficient of friction?
31) What is the difference between µs and µk?
32) If the normal force is 200 N and the coefficient of friction is 0.45, what is the force of friction (Ff)?
33) If a 5 kg box sitting on a horizontal surface has friction force of 200 N while sliding, what is µ?
Force Body Diagrams with Newton’s First Law
34) All force body diagrams for objects moving at constant speed will have a net force of ______.
35) DoesNewton’s First law apply to objects at rest? Does it apply to objects moving at constant speed?
36) Biff pushes a 24 kg bicycle with a force of 20 N without moving it. Draw a force diagram representing all the forces on the bicycle.
37) A 7 kg book slides along a table with a speed of 3 m/s. If the coefficient of friction of the table is 0.25, what applied force is needed to maintain movement at 3 m/s?
38) A 15 kg chest is on a carpet. The coefficient of friction (µ) is 0.54. What applied force is needed to keep the chest moving across the carpet at a constant speed?
39) Laura and John are pushing on a 1200kg car. The car and the driveway have a µ of 0.23. If Laura can apply a force of 1000 N, what force does John have to apply to get the car moving?
Force Diagrams and 2nd Law
40) Re-write Fnet = MA for the general situation in which you have an applied force Fa and an opposing friction force Ff.
41) For the following force body diagrams, find the acceleration for each box assuming that each box has a mass of 5 kg.
42) A 24 kg box is accelerated to the right at 5 m/s/s. If the applied force is 70 N, what does the frictional force have to be? Be sure to draw a force body diagram for a problem like this!
43) A 34 kg box is decelerated at 3.2 m/s/s. If friction is the only force acting horizontally,
a) What is the force of friction?
b) What is the coefficient of friction?
44) A 54 kg bike is accelerated to the right. The applied force is 200N and the coefficient of friction is 0.33. What is the acceleration of the bike?
Force Diagrams and 2nd Law at Angles
45) In the diagram above, what is the x-component of the 150 N applied force?
46) What is the y-component of the 150 N applied force?
47) What is the value of Fn?
48) What is the value of Fnet?
49) What is the acceleration of the box (magnitude and direction)?
Atwood Machines
50) What force pulls the system along? Assume that M1 = 3 kg and M2 = 5 kg.
51) What is the total mass of the system?
52) What is the acceleration of the system is there is no friction?
53) What is the acceleration of the system if the coefficient of friction between M1 and the table is = 0.2?
Newton’s 3rd Law
54) State Newton’s 3rd Law
55) Given an example of an action reaction pair.
56) A man pushes on a wall and the wall pushes back on him.
a) How do the magnitudes of the forces of this action-reaction pair compare to each other?
b) How do the directions of the forces of this action-reaction pair compare to each other?
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