SAMPLE EXAM FOR 2-Dimensional motion and Newton’s Laws of Motion  (CH's 3,4)

1] Let East represent the positive x axis and North the positive y axis. A constant wind with a speed of 10.0 km/hr is blowing due NE. You have a model airplane that flies at 30.0 km/hr in level flight in still air. You start its engine and release it in the direction due NW. What will be the displacement of the airplane relative to your position after it flies for 10.0 minutes?
        ANSW: 5.26 km @ 117 degrees

2] Assume the motion of a kicked football follows that of a projectile above the surface of the earth.  The ball is kicked from directly in front of the goalpost and hits the crossbar. If the ball was kicked from 20.0 m away with a velocity of 15.0 m/s at an angle of 45 degrees to the horizontal, what is the height of the crossbar?
        ANSW: 2.53 m

3] A block of mass 2.0 kg is observed to slide down an incline at a constant velocity when the incline makes an angle of 30 degrees with the horizontal. What is the coefficient of kinetic friction between the block and incline?
        ANSW: 0.58

3B]  EXPLAIN BRIEFLY which one of Newton’s three laws of motion BEST describes the above “constant velocity” situation {Credit will be given only if an explanation is included!} NOTE: All 3 laws can be applied here but ONE will best describe the state of this object.
  4] A mass of 0.50 kg is hanging vertically by a string. It is known that the string will break if the tension in it exceeds 25 N. What is the maximum acceleration that can be given to the mass by pulling up on the string?

ANSW: 40 m/s/s

Describe the condition(s) that would be required for the tension in the string to be equal to zero.
  1] A plane is flying directly over ETSU at the moment you begin this exam. The pilot is heading due West at 500 km/hr, but he is flying in a 60 km/hr wind that is blowing due South. Where will the plane be (with respect to ETSU) when the exam period is over 80 minutes from now.        

ANSW: 672 km @ 6.8 degrees SW

2] Assume the flight of a baseball follows that of a projectile above the surface of the Earth. You are the batter and hit a low pitched baseball that lands at the top of an outfield wall 85.0 meters away. If you gave the baseball a velocity of 30.0 m/s at an angle of 40.0 degrees to the horizontal, what is the velocity of the ball when it strikes the top of the wall? (ignore the initial height of the ball when you hit it)            

ANSW: 28.6 m/s @ 36.5 degrees below horizontal

4] You watch the following events happen while standing on the shore. Two sailing ships are passing your location. As you watch ship #1 pass by, moving at constant velocity, a stone is dropped from a tall mast of the ship and lands on its deck. Ship #2 passes by, moving with a constant acceleration, and a stone is also dropped from a tall mast landing on its deck. EXPLAIN, with reference to the appropriate laws of motion, where each stone (#1 and #2) lands relative to the mast from which it fell. {i.e., do they land at the foot of the mast or behind it?}

5] You are pulling a small child on a snow sled up a slope that makes a 30 degree angle with the horizontal . The combined mass of the child and sled is 20.0 kg. It is known that the coefficient of kinetic friction between the snow and sled is m k = 0.130 . If you pull the rope such that a constant force of 125 N is acting on the sled parallel to the surface of the slope, what is the acceleration of the sled/child combination up the incline?       

ANSW: +.245 m/s/s


1)  A packing crate slides down an inclined ramp at constant velocity.  Thus, we can deduce that
    a) a frictional force is acting on it.
    b) a net downward force is acting on it.
    c) it may be accelerating.
    d) it is not acted on by an appreciable gravitational force.

2)  When you sit in a chair, the sum of all the forces acting on you while you sit
    a) is up
    b) is down
    c) depends on your weight
    d) is zero

3)  If you blow up a balloon and then release it, the balloon will fly away.  This is an illustration of
    a) Newton's 1st law
    b) Newton's 2nd law
    c) Newton's 3rd law
    d) the law of gravity

4) A mass is suspended from the ceiling by means of a string.  The Earth pulls downward on the mass with the weight force
of the mass equal to 8 N.  If this is the "action" force of the 3rd law, what is the "reaction" force?
    a) the string pulling upward on the mass with an 8 N force
    b) the ceiling pulling upward on the string with an 8 N force
    c) the string pulling downward on the ceiling with an  8 N force
    d) the mass pulling upward on the Earth with an 8 N force

5) A stone is thrown horizontally from the top of a tower at the same instant another stone is dropped vertically. Which stone is traveling with the greater speed when it hits the level ground below?
    a) the dropped stone
    b) the thrown stone
    c) their speeds are the same since they will hit the ground at the same time
    d) it is impossible to determine an answer from the information given

6) If the acceleration of an object is always directed perpendicular to its velocity,
    a) then the object is speeding up
    b) then the object is slowing down
    c) the the object is changing its direction of motion
    d) then the velocity remains constant



1)  a
2)  d
3) c
4) d
5) b
6) c