Sierzega: Dynamics 1
Force as an Interaction
1.1 Observe and Represent
a) Pick up a tennis ball and hold it in your hand. Now pick up a bowling ball and hold it. Do you
feel the difference? How can you describe what you feel in simple words?
b) Think of h
Sierzega: Dynamics 1
Solutions
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1.1 Observe and Represent
a) In order to hold the bowling ball I have to push up on it a lot more than I do with the
tennis ball.
b) We could use words or arrows like in motion diagrams.
c) and
d)
Fhand on ball
b
Sierzega: Dynamics 1 Supplemental Info
Force as an Interaction
The word force is used in physics for a physical quantity that characterizes the interaction of two
objects. A single object does not have a force by default, as the force is defined through t
Sierzega: Dynamics 3
Interactions with Water: Design Experiment
Observe and Find a Pattern
You have the following equipment: a spring scale, a plastic bottle filled with sand, a container of
water, and a ruler (measuring tape).
a) Examine the equipment th
Sierzega: Dynamics 4
Motion Diagrams & Force Diagrams: How are they related?
4.1 Observe and Represent
Consider the following experiment: Mr. Sierzega is on rollerblades. One of your classmates pushes him
across the room while trying to exert a constant f
Sierzega: Dynamics 5
Inertial and Non-inertial Reference Frames
5.0 Observe and Analyze
You are sitting on a train and place a ping-pong ball on a tray table in front of you. The ping-pong ball is at
rest. All of a sudden, the ball starts rolling towards
Sierzega: Dynamics 6
Newtons Second Law: Qualitative
6.1 Observe and Find a Pattern
Student A is on rollerblades and stands in front of a motion detector. The
motion detector produces the velocity-versus-time graphs shown. Student
B (not on rollerblades)
Sierzega: Dynamics 7
Newtons Second Law: Quantitative
7.1 Observe and Find a Pattern
Imagine an experiment in which one or more identical springs pull one or more identical carts in the same
direction on a smooth horizontal track. (The springs are stretch
Sierzega: Dynamics 8
Applying Newtons Second Law
Problem-Solving Strategy for Dynamics Problems
Sketch and Translate:
Sketch the situation described in the problem; include all known information.
Choose a system object and make a list of objects that in
Sierzega: Dynamics 9
Newtons Third Law
Newtons Third Law of Motion: When two objects interact, object 1 exerts a force on object 2. Object 2 in
turn exerts an equal-magnitude, oppositely directed force on object 1:
F1 on 2 = -F2 on 1
Each force above is c
Sierzega: Dynamics 10
Friction Can Be Rough
10.1 Observe and Find a Pattern
Observe the following experiment: Rest a brick on a rough surface. Tie a string around the brick and attach a
large spring scale to it. Pull the scale slowly, pulling harder and h
Sierzega: Dynamics 11
Putting it All Together
1. Represent and Reason
You push two crates that have different masses on a smooth surface. Fill in the table that follows for the two
situations. Use the rule that relates the forces that two objects exert on