1. Circle the right answers. There is only one correct answer for each question.

I. What is the normal force exerted by the table on the book if both of them are accelerating upward with an acceleration of 3 m/s2 ? Mass of the book is 2 kg.

A. 6N

B. 13.6N

C. 19.6N

D. 25.6N

E. None of above

II. A football is kicked at ground level with a speed of 25 m/s at an angle of 30o. The football hits the ground at the same level later. Which of the following statement is not correct?

A. The football will have the same range if it is kicked at an angle of 60o with the same speed (25 m/s).

B. The velocity of the football is zero when it is at the highest point.

C. The football is always accelerating downward with an acceleration of 9.8 m/s2, until it hits the ground.

D. The horizontal component of the football=s velocity is always 25 cos 30o m/s.

E. The football will hit the ground with the same speed of 25 m/s.


III. How many different forces are acting on the lower block? All surfaces are rough. Consider friction and normal force as two different forces.

A. 7

B. 6

C. 5

D. 4

E. 3


IV. The coefficient of static and kinetic friction between the block and the horizontal surface are 0.35 and 0.25 respectively, what is the frictional force acting on the block?

A. 19.6 N

B. 6.86N

C. 4.95N

D. 3N

E. None of above.


V. Which of the following is not a proper explanation to the observation:
Observation Explanation
A A spaceship in outerspace (far from any other astronomical objects) has to travel with constant velocity, if no rocket is fired.  Newton=s first law of motion. 
B Projectile motion is independent of mass.  All objects have the same acceleration due to gravity, g=9.8 m/s2. 
C For a person standing on the ground, the normal force from the floor equals to the weight of the person in magnitude.  Action and reaction are equal in magnitude. 
D The unit Newton (N) is equivalent to kgm/s2.  F = ma.
E As a car is turning around a corner, the net force acting on the car cannot be zero.  Both Newton=s first law and second law imply that the net force acting on an object cannot be zero if it is not moving with a constant velocity.