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Physics 1401 Test 2 Summer 1 2007
1-4 5pts each
1. Jack’s pet fly is tethered to a button on Jack’s shirt by a string. The fly is flying in a
circular path with a constant speed. Which of the following is true? The fly has
a) Constant velocity and constant acceleration
b) Changing velocity and constant acceleration
c) Constant velocity and changing acceleration
d) Changing velocity and changing acceleration
NOTE: Both velocity and acceleration are vectors.
2. Which of the following is a statement of Newton’s Third Law of Motion?
a) For every force acting on an object, there is a reaction force equal in magnitude and
opposite in direction acting on a different object.
b) F = ma
c) An object with constant speed will maintain that constant speed until acted upon by a
net external force.
d) An object with constant velocity will maintain that constant velocity until acted upon
by a net external force.
3. You are standing on a scale in an elevator. The elevator is ascending at a constant rate.
The reading on the scale would be ______________?
a) equal to your mass
b) equal to your weight
c) greater than your mass
d) greater than your weight
e) less than your weight
4. You are standing on a scale in an elevator. The elevator is moving down from the
second floor to the first floor. While the elevator is slowing to a stop on the first floor the
reading on the scale would be _________________?
a) equal to your mass
b) equal to your weight
c) greater than your weight
d) less than your weight
5. In the diagram above m2>m1. If the masses are released, please use force methods to,
find an equation for the acceleration of the blocks in terms of the two masses and the
acceleration due to gravity. (15pts: 6 for free body diagrams, 6 for Newton’s 2nd Law
equations and 3 for being able to find the acceleration)
6. A 2kg box rests on a plank that is inclined at an angle of 65° above the horizontal.
The upper end of the box is attached to a spring with force constant k = 360N/m, as
show in the figure above. If the coefficient of static friction between the box and the
plank is 0.22, by how much is the spring stretched?
Hints: You are to assume the force of static friction is at max. Also note that if
friction is reduced the spring will pull the box up the incline.
(15pts: 6pts for FBD. 6Pts NSL 3pts algebra)
THE REMAINDER OF THE TEST SHOULD BE WORKED USING THE WORK
AND ENERGY METHODS FROM CHAPTER 7&8. You may also need the
methods from chapters 5&6 but they are not sufficient to solve the remaining
problems.
7. On October 31, 1972 a 10kg meteorite was imbedded in the hood of a car in
Podunk Arkansas, creating a 0.22m deep dent. If the initial speed of the meteorite was
550m/s, what was the force exerted by the car on the meteorite? (10 pts)
8. Calculate the power of a 0.0013kg fly as it walks straight up a windowpane at
0.025m/s. (10 pts)
9. Tarzan swings (from rest) on a 30m long vine inclined at an angle of 37° with the
vertical. Find his speed at the bottom of the swing? (10 pts)
10. The block above is used to compress the spring (k=350N/m) shown a distance of
0.07m then is released from rest. As it slides from A to B it encounters a rough
section of length 0.1m and coefficient of kinetic friction equal to 0.3. Find the speed
of the block at B. Then find the distance up the incline (measured along the incline)
the block travels before coming to rest. The inclination of the incline is 25°. All
surfaces are assumed to be frictionless except the small (0.1m) section between points
A and B. (20 pts)