Name: 
 

Physics 12 - Unit 1 Test



True/False
Indicate whether the sentence or statement is true or false.
 
 
For questions 1 to 6, consider a ball of mass m, thrown at an angle above the horizontal and undergoing projectile motion under negligible air resistance.
 

1. 

The time for the ball to rise equals the time for the ball to fall to the same horizontal level.
 

2. 

The net force on the ball at the top of its flight is zero.
 

3. 

The acceleration of the ball on the way up equals the acceleration on the way down.
 

4. 

After leaving your hand and before landing, the speed of the ball is at a minimum at the top of its trajectory.
 

5. 

      The magnitude of the horizontal component of the velocity of the ball just before impact exceeds the magnitude of the horizontal component of the velocity just after the ball leaves your hand.
 

6. 

The magnitude of the acceleration of the ball at the top of its trajectory equals the ratio of the weight of the ball to its mass.
 
 
or questions 7 to 12, assume that you are twirling a small rubber stopper of mass m (at a constant speed v) tied to a string in a vertical circle as shown in Figure 1.
p12u1_files/i0090000.jpg

Figure 1
For questions 7 to 12
 

7. 

At position 3, the direction of the instantaneous acceleration is westward and the direction of the instantaneous velocity is upward.
 

8. 

The vector quantity p12u1_files/i0110000.jpg is closest to the instantaneous acceleration as the stopper moves from position 6 to position 1.
 

9. 

The magnitude of the tension in the string at position 1 exceeds the magnitude of the tension at position 4 by an amount equal to mg.
 

10. 

At position 5, the force that causes the stopper to accelerate toward the centre of the circle is the sum of the force of tension in the string and a component of the force of gravity on the stopper.
 

11. 

If you release the ball at the instant it reaches position 1, the instantaneous velocity of the stopper just after the release will have a small upward component and a large eastward component.
 

12. 

For a constant radius and frequency of revolution of the stopper, the magnitude of the centripetal acceleration is directly proportional to m.
 

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 
 
Questions 13 to 18 relate to the situation in Figure 2, in which a child on a toboggan (a system of total mass m) accelerates down a hill of length L inclined at an angle q to the horizontal in a time interval p12u1_files/i0170000.jpgt. The +x and +y directions are labelled on the diagram. Assume that friction is negligible unless indicated.
p12u1_files/i0170001.jpg

Figure 2
For questions 13 to 18
 

13. 

The magnitude of the child’s acceleration down the hill is
a.
p12u1_files/i0180000.jpg
b.
p12u1_files/i0180001.jpg
c.
g sin p12u1_files/i0180002.jpg
d.
g cos p12u1_files/i0180003.jpg
e.
g tan p12u1_files/i0180004.jpg
 

14. 

The magnitude of the child’s average velocity is
a.
p12u1_files/i0190000.jpg
b.
p12u1_files/i0190001.jpg
c.
p12u1_files/i0190002.jpg
d.
p12u1_files/i0190003.jpg
e.
p12u1_files/i0190004.jpg
 

15. 

The magnitude of the force exerted by the toboggan on the hill is
a.
mg
b.
mg cos p12u1_files/i0200000.jpg
c.
mg sin p12u1_files/i0200001.jpg
d.
mg tan p12u1_files/i0200002.jpg
e.
p12u1_files/i0200003.jpgmg sin p12u1_files/i0200004.jpg
 

16. 

If the child starts from rest and accelerates uniformly down the hill, the time required to reach the bottom of the hill is
a.
Lg sin p12u1_files/i0210000.jpg
b.
2Lg sin p12u1_files/i0210001.jpg
c.
p12u1_files/i0210002.jpg
d.
p12u1_files/i0210003.jpg
e.
p12u1_files/i0210004.jpg
 

17. 

If p12u1_files/i0220000.jpgav is the average velocity and p12u1_files/i0220001.jpg is the instantaneous velocity, then at the halfway point in the journey down the hill
a.
|p12u1_files/i0220002.jpgav| = |p12u1_files/i0220003.jpg|
b.
|p12u1_files/i0220004.jpgav| > |p12u1_files/i0220005.jpg|
c.
|p12u1_files/i0220006.jpgav| < |p12u1_files/i0220007.jpg|
d.
|p12u1_files/i0220008.jpgav| and |p12u1_files/i0220009.jpg| can be compared only if we are given numerical data.
e.
p12u1_files/i0220010.jpgav  and p12u1_files/i0220011.jpg cannot be meaningfully compared, since the object in question is on an inclined plane .
 

18. 

If the situation in Figure 2 is changed so that there is a coefficient of kinetic friction mK between the toboggan and the hill, then the magnitude of the child’s acceleration down the hill is
a.
g(sin p12u1_files/i0230000.jpg p12u1_files/i0230001.jpg mK cos p12u1_files/i0230002.jpg)
b.
g(sin p12u1_files/i0230003.jpg + mK cos p12u1_files/i0230004.jpg)
c.
p12u1_files/i0230005.jpg
d.
g(mK cos p12u1_files/i0230006.jpg p12u1_files/i0230007.jpg sin p12u1_files/i0230008.jpg)
e.
none of these