Cycle I Advanced Placement Physics B

John Dewey High School

Mr. Klimetz

Newton's Laws of Motion

and the Construction and

Interpretation of Free-Body

Diagrams

Laboratory No. 8

Newton's Laws of Motion

Solve each of the following problems in the spaces provided or on a separate sheet of paper. Freely consult your class notes and Reference Tables for Physics as needed. Show all work including variables, equations, and substitutions. Highlight your answers and remember to express them with appropriate units.

1.  A 400.-kg mass is accelerated from rest to 80.0 m/s in 16 s. Neglecting friction, calculate

(a) the acceleration experienced by the mass, and

(b) the applied force necessary to accelerate the mass.

2.  A force of 15,000 N is applied by the brakes to the wheels of a car traveling at 30. m/s in a straight line on a horizontal frictionless racetrack. If the car is brought to rest in precisely 15 s, calculate

(a) the acceleration experienced by the car, and

(b) the car's mass.

3.   How much force is being applied to a 35,000 kg bus by its engine while traveling north on Harway Avenue from 27th Avenue to 26th Avenue while traveling at a speed of 10. m/s? [Neglect friction.]

4.  A force of 1200 N is applied to a bullet by the rifle from which it was fired. The bullet possesses a muzzle velocity of 1500 m/s and the length of the rifle barrel is 1.0 m. Based on this data calculate

(a) the acceleration of the bullet,

(b) the mass of the bullet,

(c) the time the bullet spent traveling through the barrel after the trigger was pulled, and

(d) the magnitude of the force applied to the rifle by the bullet.

5.  Which possesses the greater inertia - 4.00 kg of steel at rest or 4.00 kg of styrofoam at rest?

6.  A 50,000 kg train engine traveling east at 20.0 m/s collides with a 10,000 kg flatcar traveling at 1 m/s west. Both cars lock together after they collide. Based on this information calculate

(a) the initial momentum of the engine,

(b) the initial momentum of the flatcar, and

(c) the final velocity of the locked cars.

7.  A 0.20 kg frictionless hockey puck traveling at 30. m/s south is struck by a goalie with an impulse of 20. N-s and returned due north to the opposing team goalie over a distance of 35 m. Based on this information calculate

(a) the initial momentum of the hockey puck traveling south,

(b) the final speed of the hockey puck traveling north, and

(c) the time of travel of the hockey puck between the goalies.

Free-Body Diagrams

A free-body diagram is a useful dynamic analysis tool which permits system(s) of concurrent forces (force pairs) acting on an object to be graphically represented, their sums more simply calculated, and the response of the object to those force sums (net forces) more easily interpreted and understood. Based on the information provided in class and your reading of Chapter 7 in the textbook, produce a free-body diagram for each of the situations provided below. Each diagram should be labeled with arrows representative of each of the forces acting on the object of interest. Additionally, you should also predict the response of the object to the system(s) of concurrent forces based on an interpretation of your free-body diagram. That is, what sort of motion will the object experience in response to the forces applied to it? Provide mathematical data and calculations to support your interpretations.

1.  A box with a mass of 40.0 kg is resting on a horizontal surface.

2.  A box with a mass of 30.0 kg is placed on a frictionless horizontal surface. A pulling force of 15.0 N is applied to the right side of the box.

3.  A box with a mass of 50.0 kg is placed on a frictionless plane inclined at 30 degrees from the horizontal.

4.  A box with a mass of 20.0 kg is placed on a 30-degree inclined plane. The coefficient of starting friction between the box and the plane is 0.720.