Test Physic 1401

PHYS 1401 College Physics I Test 2 Page 1 of 6 Houston Community College System
PHYS 1401
Test # 2 PHYS 1401 College Physics I Test 2 Page 2 of 6
Name ______________________________________________________ Date ____________
PHYSICS 1401. Test 1
Chapters 3, 4 and 5
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INSTRUCTIONS:
Answer all questions from Section I (2 points per question).
And
Solve at least four problems from Section II (20 points per problem).
More than four problems from Section II can be attempted. However, points will be awarded for only the best four answers.
NOTE: Credit will only be given for answers accompanied by work carried out. Therefore, make sure all calculations are attached to the test.
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Section I
1. A student adds two vectors with magnitudes of 200 and 40. Which one of the following is the only possible choice for the magnitude of the resultant?
a. 100
b. 200
c. 260
d. 40
2. A car is initially moving at 20 m/s east and a little while later it is moving at 10 m/s north. Which of the following best describes the orientation of the average acceleration during this time interval?
a. northeast
b. northwest
c. west
d. north of west
3. A baseball is thrown by the center fielder (from shoulder level) to home plate where it is caught (on the fly at shoulder level) by the catcher. At what point is the magnitude of the acceleration at a minimum? (air resistance is negligible)
a. just after leaving the center fielder’s hand
b. just before arriving at the catcher’s mitt
c. at the top of the trajectory
d. acceleration is constant during entire trajectory PHYS 1401 College Physics I Test 2 Page 3 of 6
4. If we know an object is moving at constant velocity, we may assume:
a. the net force acting on the object is zero.
b. there are no forces acting on the object.
c. the object is accelerating.
d. the object is losing mass.
5. An astronaut applies a force of 500 N to an asteroid, and it accelerates at 7.00 m/s2. What is the asteroid’s mass?
a. 71 kg
b. 135 kg
c. 441 kg
d. 3 500 kg
6. A thrown stone hits a window, but doesn’t break it. Instead it reverses direction and ends up on the ground below the window. In this case, we know:
a. the force of the stone on the glass > the force of the glass on the stone.
b. the force of the stone on the glass = the force of the glass on the stone.
c. the force of the stone on the glass < the force of the glass on the stone.
d. the stone didn’t slow down as it broke the glass.
7. As a car skids with its wheels locked trying to stop on a road covered with ice and snow, the force of friction between the icy road and the tires will usually be:
a. greater than the normal force of the road times the coefficient of static friction.
b. equal to the normal force of the road times the coefficient of static friction.
c. less than the normal force of the road times the coefficient of static friction.
d. greater than the normal force of the road times the coefficient of kinetic friction.
8. When an object is dropped from a tower, what is the effect of the air resistance as it falls?
a. does positive work
b. increases the object’s kinetic energy
c. increases the object’s potential energy
d. None of the above choices are valid.
9. A Hooke’s law spring is compressed 12.0 cm from equilibrium and the potential energy stored is 72.0 J. What is the spring constant in this case?
a. 10 000 N/m
b. 5 000 N/m
c. 1 200 N/m
d. No answer is correct.
10. The unit of power, watt, is dimensionally the same as:
a. joule-second.
b. joule/second.
c. joule-meter.
d. joule/meter. PHYS 1401 College Physics I Test 2 Page 4 of 6
Section II
11. A ball is rolled horizontally off a table with an initial speed of 0.24 m/s. A stopwatch measures the ball’s trajectory time from table to the floor to be 0.30 s. Assume air resistance to be negligible and an acceleration due to gravity g = 9.8 m/s2 to calculate:
a. the height of the table (10 points)
b. the velocity of the ball (magnitude and direction) as it hits the floor below (10 points).
12. Three identical 6.0-kg cubes are placed on a horizontal frictionless surface in contact with one another. The cubes are lined up from left to right and a 36-N force is applied to the left side of the left cube causing all three cubes to accelerate to the right. If the cubes are each subject to a frictional force of 6.0 N, calculate:
a. the acceleration of the blocks (10 points)
b. the magnitude of the force exerted on the middle cube by the left cube in this case (10 points) PHYS 1401 College Physics I Test 2 Page 5 of 6
13. A 5 000-N weight is suspended in equilibrium by two cables. Cable 1 applies a horizontal force to the right and has a tension, T1. Cable 2 applies a force upward and to the left at an angle of 37.0° to the negative x-axis and has a tension, T2. Find:
a) T2 (15 points) and
`` b) T1 (5 points)
14. A girl and her bicycle have a total mass of 40.0 kg. At the top of the hill her speed is 5.0 m/s, and her speed doubles as she rides down the hill. The hill is 10.0 m high and 100 m long. Calculate:
a. the mechanical energy lost to friction (15 points)
b. the force of friction exerted on her bicycle by the road surface (5 points) PHYS 1401 College Physics I Test 2 Page 6 of 6
15. A 10-kg block rests on a level surface and is attached by a light string to a 6.0-kg hanging mass where the string passes over a massless frictionless pulley. If g = 9.8 m/s2, and the coefficient of kinetic friction between the level surface and the block is 0.30, calculate:
a) the acceleration of the hanging mass (10 points)
b) the tension in the connecting string (10 points)