Undergraduate Mechanics Page - Some Questions
Ralph Shiell, Physics Department, Trent University, Ontario
Welcome. Below you will find a few mechanics questions suitable for all physics students from 1st year undergraduate upwards.
There are seven questions in total. Think about all of them before clicking on the link at the bottom of the page.
Three suggestions:
i) Remember that no-one knows the answer to any question instantaneously. Even Nobel laureates need some time to figure out an answer.
ii) I strongly suggest you don't just get the "right" answer(s). Please spend some time figuring out why all the other answers are not correct. This is probably more important than simply getting the right answer.
iii) If nothing else, I suggest you sketch the physical problem posed by each question. It is generally the only way that you can be sure you have understood what the question is asking, and it will assist you when you come to look at the notes and solutions page which (intentionally) does not have the questions listed on it.
(For those of you who are supremely confident, then I suggest you check that your total mark comes to 22, using the key below, before clicking on the link at the bottom of the page:
- (a) is worth 4 points
- (b) is worth 3 points
- (c) is worth 2 points
- (d) is worth 1 point )
1. A vector in physics is something with (more than one answer might be correct):
a) position
b) magnitude
c) direction
2. For a system of particles, which of the following is generally conserved (more than one answer might be correct)?
a) total energy
b) linear momentum
c) angular momentum
d) a system can usually change all of the above
3. Consider a particle with position vector as a function of time given by r(t) = (t, 2t, 2). If the units of distance are in metres, which of the following has the largest value at t = 1 sec (more than one answer might be correct)?
a)
b)
c)
d) the question is meaningless
4. If the rigid solid cylinder is rotating about the axis shown, what can be said about the motion of any point within the cylinder?
a) each point on the cylinder follows a circular path and has the same angular speed, ω
b) each point follows (in general) an elliptical path, and the angular speed, ω, is meaningless in this case
c) each point follows a circular path with, in general, a different angular speed, ω
5. The angular momentum of particle B about point A in the picture above does the following (more than one answer might be correct) :
a) takes the same value at all times
b) changes in a way I could calculate if I knew the physical quantities (mass, velocity, distance etc.) of this system
c) increases as B approaches A and decreases as B moves further away
6. Ross suggests making a hydrogen atom by shooting an electron towards a proton so that they get close enough to attract each other permanently. Sandra says that Ross is missing something and it won't work.
a) Sandra is too pessimistic - a hydrogen atom contains an electron and a proton, so everything is ok
b) Sandra is right
7. A hockey puck with glue on its rim travelling along the x axis hits a dumbbell made from two hockey pucks joined by a light stick as shown above. After the inelastic collision the motion of the resulting dumbbell is :
a) to the left, always parallel to the x axis, and rotating in a clockwise direction when seen from above
b) to the left, typically at some angle to the x axis, and rotating in a clockwise direction when seen from above
c) to the left at some angle to the x axis and rotating in an anti - clockwise direction when seen from above
d) to the left at some angle to the x axis and not rotating at all
To see the solutions to these questions, then click here
If you have any comments on these pages, please email me.
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