Newton Laws Notes by mikesanye

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									2011 2nd Trimester Honors Notes


                                  Newton’s Laws Notes
                                                             Name ________________
   1. What is inertia?



   2. What is a force?


          a. What is it measured in?


          b. What is a freebody diagram? Draw one for a sign hanging.




   3. Newton’s 1st law



          a. Draw a free body diagram for an elevator moving upwards at a constant
             speed.



   4. Consider an elevator going upwards at a constant speed. The force of the rope on
      the elevator is __________ the force of
      gravity on the elevator.
          a. Greater than
          b. Less than
          c. The same as

   5. The distance between two telephone poles is 50.0m. When a 1.00 kg bird lands
      on the telephone wire midway between the poles, the wire sags 0.200 m.
                      a. Draw a freebody diagram of the bird




          b. Write Net Force vector equations.
2011 2nd Trimester Honors Notes


          c. How much tension does the bird produce in the wire?




   6. 1st Law Demonstrations:




   7. Newton’s Second Law




          a. If you squeeze a dry sponge what changes?
             Mass, volume, Inertia, density


                b. If an object is accelerating what are its possible motions?


                c. What is the force due to gravity?




                  d. A diver dives into water, the water slows him to a stop. How do
                     the force of water and gravity compare?




           8. If you drop a feather and a hammer on the moon, which will
              strike the surface first? Use Newton’s 2nd law to explain why.
2011 2nd Trimester Honors Notes


    9. A performer in a circus is fired from a cannon as a
       “human cannonball” and leaves the cannon with a
       speed of 18.0 m/s. The performer’s mass is 80.0 kg.
       The cannon barrel is 9.20m long. Find the average
       net force exerted on the performer while he is being
       accelerated inside the cannon.




                                                            




    10. An airplane accelerates uniformly from rest. A physicist passenger holds up a thin string of
        negligible mass to which she has tied her ring, which has a mass m. She notices that as the plane
        accelerates down the runway, the string makes an angle  with the vertical as shown above.
a. In the space below, draw a free-body diagram of the ring, showing and labeling all
   the forces present.




The plane reaches a takeoff speed of 65 m/s after accelerating for a total of 30 s.
b. Determine the minimum length of the runway needed.




c. Determine the angle B that the string makes with the vertical during the acceleration of
the plane before it leaves the ground.
2011 2nd Trimester Honors Notes


   11. How do the tensions in the ropes compare?




              a. If the blocks are 10 kg each and are pulled by a force of 100 N what is
                 the acceleration of the system?




              b. Find the tension between each of the blocks.




   12. Three objects are connected by light strings. The string connecting the 4.00 kg
       object and the 5.00 kg object passes over a light frictionless pulley.
           a. Draw a freebody diagram for each of the three objects.




 5 kg mass                        4 kg mass                          3 kg mass
                               nd
          b. Write the Newton 2 law equations for all three objects.
2011 2nd Trimester Honors Notes


          c. Find the acceleration of each object.




          d. Find the tension in rope connecting the 5 kg and 4 kg masses.




          e. Find the tension in the rope connecting the 4 kg and 3 kg masses.




   13. A 20N thrust is exerted on a 0.50 kg rocket for a time interval of 8.0 s. The
   rocket then coasts upward more distance until its speed is reduced to zero. Determine
   the maximum height of the rocket.
           a. Draw a freebody diagram during launch




                      b. Write Newton’s 2nd law equations




          c. Find the velocity of the rocket after 8.0 seconds.
2011 2nd Trimester Honors Notes


          d. Find the height of the rocket after 8.0 seconds.




          e. Find the maximum height of the rocket




   14. What is the normal force?


              a. If you press down on a book what happens to the normal force?




              b. What is the direction of the normal force if a book is pressed to a wall?




   15. Arlo pushes a crate with 100 N and there is a frictional force of 20N against the
   crate. The crate has a mass of 50 kg, find the acceleration of the crate.
     a. Draw a freebody diagram




     b. Write Newton 2nd Law equations




              c. Solve Newton 2nd Law equations
2011 2nd Trimester Honors Notes


   16. A icy hill is inclined at an angle of 30 degrees. Determine
   the acceleration of a car on that hill if it starts at rest.
              a. Draw a free body diagram




              b. Write Newton’s 2nd law equations




              c. What is the acceleration of the car?




   17. Arlo is on an elevator. His mass is 72.2 kg.
              a. Draw a free body diagram.



              b. What is the scale reading when the elevator is at rest?



              c. If the elevator (starting from rest) reaches 3m/s in a time of 2 seconds
              what is it’s acceleration?




                           d. What does the scale read during part “c”? (If the elevator
                           is moving upwards)
2011 2nd Trimester Honors Notes


              e. If the elevator stays at 3 m/s for 5 seconds what does the scale read?




           f. If the elevator slows to rest in 4 seconds, what does the scale read?




           g. When did Arlo feel the “lightest”, the “heaviest”?




18.




The hanging block is 3kg, the block on the ramp is 5kg. The angle of the ramp is 30
degrees.
       a. Draw the free body diagram for each block.




       b. What is the acceleration of the blocks?




       c. What is the tension in the cord?
2011 2nd Trimester Honors Notes


   19. The three blocks of masses 10.0 kg, 5.00 kg, and 3.00 kg are connected by light
       strings that pass over frictionless pulleys as shown. The acceleration of all of the
       blocks is 2.00 m/s2 to the left, and the surfaces are rough.
                            5.00 kg
                                               3.00 kg

            10 kg                               200

                    a. Draw a free body diagram for each block




        10 kg                            5 kg                          3 kg


                    b. Write Newton’s 2nd Law equations for each block
10 kg                                       5 kg                              3 kg




                       20. Newton’s Third Law



           a. Horse and Cart




           b. If the Earth exerts 1000N on an orbiting communications satellite what is
              the force on the Earth by the satellite? Why doesn’t the Earth orbit the
              satellite?
2011 2nd Trimester Honors Notes


21. If a Mack truck and a Volkswagen have a head on collision, which vehicle will
experience the greater impact force?
                   a. The mack truck
                   b. The Volkswagen
                   c. Both the same
                   d. It depends on other factors.

22. Alice is standing on ice and is holding a rope connected to a sled. If Alice pulls with
a force of 2N, what force does the sled exert on Alice?




        a. Do Alice and the sled have the same acceleration? If Alice’s mass is 45 kg,
what is her acceleration? If the sled is 10 kg what is its acceleration?




                 23. Consider a car at rest. We can conclude that the downward
                 gravitational pull of Earth on the car and the upward contact force of
                 Earth on it are equal and opposite because
                                        a. The two forces form an interaction pair (3rd
                                             law)
                                        b. The net force on the car is zero (2nd law)
                                        c. Neither of the above


24. Two types of friction
    a. Static friction




   b. Kinetic Friction




25. Demonstration
2011 2nd Trimester Honors Notes


26. For each of the following, draw a freebody diagram and write Newton 2nd Law
equations.
           a. You press your physics                       d. Alice pushing a filing
               textbook flat against a                        cabinet but it doesn’t
               vertical wall with your                        move.
               hand.




           b. A 10 kg block is at rest                    e. A hock puck sliding on
              on an inclined plane.                          ice and slowing down




           c. A block is sliding down                     f. Arlo pulling a crate with
              an inclined plane                              a force at a 30 degree
                                                             angle with the horizontal
                                                             and at a constant speed
2011 2nd Trimester Honors Notes


   27. Bock B weighs 711 N. The coefficient of static friction between block and table
   is 0.25; assume that the cord between B and the knot is horizontal.

                       knot
                              30
          B


                          A




          a.   Draw a free body for block B, block A and the knot.
Block B                     Block A                              Knot


          b. Write all Newton 2nd law equations
Block B                    BlockA                                Knot




          c.   Find the maximum weight of block A for which the system will be
               stationary.
2011 2nd Trimester Honors Notes


28. A 1000N crate is being pushed across a level floor at a constant speed by a force F of
300N at an angle of 20 degrees below the horizontal.




           b. Draw a freebody diagram




           c. Write Newton 2nd Law equations




           d. What is the coefficient of kinetic friction between the crate and the floor?




           e. If the 300 N force is instead pulling the block at angle of 20 degrees above
              the horizontal what will be the acceleration of the crate?
2011 2nd Trimester Honors Notes



29.
                        100N



                                              50N
      a. Draw a freebody diagram for each block




      b. What is the minimum force of friction required to hold the system in equilibrium?




      c. What coefficient of static friction between the 100 N block and the table ensures
         equilibrium?




      d. If the coefficient of kinetic friction between the 100N block and the table is 0.250,
         what hanging weight should replace the 50.0N weight to allow the system to
         move at a constant speed once it is set in motion?
2011 2nd Trimester Honors Notes




   30. A 5.0 kg penguin sits on a 10 kg sled. A horizontal force of 45 N is applied to the
   sled, but the penguin attempts to impede the motion by holding onto a cord attached
   to a tree. The coefficient of kinetic friction between the sled and snow as well as that
   between the sled and the penguin is 0.20.
               a. Draw a free-body diagram for the penguin and one for the sled.




            Penguin                                   Sled

              b. Identify the reaction force for each force in your diagrams.




              c. Find the tension in the cord




              d. Find the acceleration of the sled.
2011 2nd Trimester Honors Notes


                                  Homework – Newton
                                                             Name__________________
1. If you were in a spaceship and launched a cannonball into frictionless space, how
much force would have to be exerted on the ball to keep it going?




2. If you hold a coin above your head while in a bus that is not moving, the coin will
land at your feet when you drop it. Where will it land if the bus is moving in a
straight line at constant speed? Explain.




           3. Many automobile passengers suffer neck injuries when struck by cars from
           behind. How does Newton’s law of inertia apply here? How do headrests
           help to guard against this type of injury?




4. If an elephant were chasing you, its enormous mass would
be very threatening. But if you zigzagged, the elephant’s
mass would be to your advantage. Why?




              5. In the cabin of a jetliner that cruises at 600 km/h, a pillow drops from
              an overhead rack into your lap below. Since the jetliner is moving so fast,
              why doesn’t the pillow slam into the rear of the compartment when it
              drops? What is the horizontal speed of the pillow relative to the ground?
              Relative to you inside the jetliner?

								
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