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Study Guide: Newton’s 3 Laws of Motion and Vector Addition
Ch. 4 in Your Book
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Be able to add vectors and solve riverboat problems.
State Newton’s 1st, 2nd, and 3rd laws of motion.
Use Newton’s 1st Law of motion to explain various situations.
Why does a skateboarder fly forward when his skateboard hits the curb?
What is inertia?
Draw free-body diagrams for various situations, labeling all forces.
Use Newton’s 2nd Law of motion to solve force problems
Can be asked to solve for weight (Fg), FN, Fa, Ff, FNet, acceleration, and mass
Use the relationship between the force of friction (Ff), the coefficient of friction (), and the
normal force (FN) to solve for an unknown variable.
Know the difference between static and kinetic friction.
Use Newton’s 3rd Law of motion to identify action reaction pairs.
You will be required to draw a free-body diagram for each problem on the test so practice doing it for
each problem below.
1. A 75 kg man in an elevator experiences a normal force of 650 N. What is the acceleration of the
elevator he is in? (Ans: -1.14 m/s2)
2. A force of 9,375N is applied horizontally to an 800 kg car to move it across a horizontal road. The car
is moving with a constant velocity. What is the coefficient of friction? Is this static or kinetic friction?
(Ans: 1.2)
3. A 7kg box is pushed across a room at a constant velocity. The coefficient of friction between the box
and floor is 0.4. What is the applied force on the box? (Ans: 27.44 N)
4. A 14kg desk sits on the floor at rest. The maximum coefficient of static friction is 0.6. What is the
maximum force that James can apply to the box before it begins to move? (Ans: 82.32 N)
5. Carl pushes a 400N box that has a coefficient of kinetic friction of 0.5. The box accelerates at a rate of
1.3m/s2.
What is the force of friction acting on the box? (Ans: 200N)
What is the net force acting on the box? (Ans: 53.04N)
What is the applied force acting on the box? (Ans: 253.04N)
6. Mr. Clause attempts to pull a 600N bag of toys across his living room floor by applying a force of
400N. Calculate the coefficient of kinetic friction between the bag and floor if the bag accelerates at a
rate of 1.3 m/s2. (Ans: 0.53)
7. Steve pushes his 8000 N car with a force of 5000 N. If the car accelerates at 2.4 m/s2 then what is the
coefficient of kinetic friction between the road and car tires? (Ans: 0.38)
8. a. Draw a free-body diagram for an apple falling at a constant velocity. Consider air resistance.
b. Draw a free-body diagram for a falling apple accelerating downward. Consider air resistance.
c. Draw a free-body diagram for a car braking to a stop.
Vector practice problems are on the next page.
9. A boat travels North across a 100� wide river at 12 m/s. If the water is flowing West at 4m/s,
a. What is the resultant velocity of the boat? (12.6 m/s @ 18.4 W of N)
b. How much time does it take the boat to reach the other side of the river? (8.3 s)
c. How far downstream will the boat be when it reaches the other side? (33.2 m)
10. A car drives 7�� East, then drives 3�� South, then drives 4�� West, and finally it drives
another 6�� South.
a. What is the total distance the car travelled? (20 km)
b. What is the displacement of the car? (9.5 km @ 71.6 S of E)