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This is the Past Paper of General Physics which includes Momentum Conserved, Motion of Objects, Different Paths, Relative Speeds, Conservative Force, Mass of Spring Board, Kinetic Energy, Gravitational Potential Energy etc. Key important points are: Lifting Force, Gravitational Force, Constant Speed, Kinetic Energy, Potential Energy, Zero Point? for Reference, Net Work Done, Conservation of Energy Equation, Nal Velocity, Energy Techniques
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St. Vincent College PH 111: General Physics I
The exam consists of 4 questions. There will be 50 minutes to complete the exam. The questions may not be worth the same number of points, read the entire exam before beginning work. Put your name on all pages.
Problem 1 25
Problem 2 30 Problem 3 25
Problem 4 20
Total 100
a) (5 pts) A system exists on which no net work is done. Is it possible to tell from this information whether or not it is an isolated system?
b) (5 pts) An object is lifted at a constant speed against the gravitational force. The lifting force does work on the object yet the kinetic energy of the object does not change. Explain where this energy goes.
c) (5 pts) When calculating gravitational potential energy, one must choose a “zero point” for reference. For example, when using U = mgh, the potential energy is zero wherever h = 0. Where is the “zero point” when using the more general form for gravitational potential energy,
U (r) = −
Gm 1 m 2 r
d) (5 pts) Explain one method that could be used to determine whether or not friction is a conservative force.
e) (5 pts) If more energy enters a system than exits, list a few of the possible consequences.
U (x) = (x − a)^2 (x + a)^2
and is shown in the plot below, where a is a constant.
U (x)
Position
Energy
-2a -a^0 a^ 2a
a^4
2 a^4
a) (10 pts) Identify the equilibrium position(s) and indicate the type of equilibrium. (You may do this on the plot if you wish.)
b) (5 pts) If the total energy of the system is a^4 / 2 , in what regions of space may the system exist (ie. what are the allowed possible values of x)? You may estimate the values from the graph rather than actually solving for them.
c) (5 pts) If the total energy of the system is the same as in part (b), what is the kinetic energy of the system when the location is x = −a?
d) (5 pts) From the expression for the potential given above, derive an expression for the force (as a function of position) related to this potential.
a) (10 pts) After the first hop the bottom of the pogo-stick achieves a vertical displacement of 50 cm. The person/pogo-stick then fall straight down. When the bottom of the pogo-stick makes contact with the ground, the spring starts being compressed. If the person (along with the pogo-stick) has a mass of 40 kg and the spring constant is 3500 N/m, how far is the spring compressed when the person finally stops moving down?
b) (10 pts) On the second hop, starting with the spring compressed from part (a), the person holds onto the pogo-stick and jumps upwards with an additional constant force of 400 N. How high to they go on this second jump? (Note that the upward force exerted on the person from their jump will end at the same point at which the spring is no longer compressed.)
