PHY 201/211 General Physics

PHY 201/211 General Physics Even Sections. 11:00-11:50 lecture Final Examination

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Answer all problems.

Do not start working until you are told to do so.

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formula sheets are also provided at the back of this test.

(Do not write below)

Problem No.	Score
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Total

1. (25points)

Circle the right answers. Only one choice is correct. No penalty for wrong guess.

I. A ball is thrown upward. It falls back after reaching the highest point. Which statement is not correct?

A. v = 0 m/s at the highest point.

B. When the ball is falling down, acceleration must be negative in sign.

C. Velocity changes sign as the ball goes through the highest point.

D. Acceleration and velocity have opposite sign when the ball is going up.

E. Acceleration and velocity have the same sign when the ball is coming down.

II. In Earth's gravitational field, which force is forming an action-reaction pair with the weight of the 10kg block?

A. Force exerted on the 20kg block due to the 10kg's weight.

B. Weight of the 20kg block.

C. Normal force from the table top.

D. Normal force from the 20kg block on the 10kg block.

E. Gravitational pull on Earth due to the 10kg block.

III. The gravitational attraction between two objects is F. What will be the attraction if the separation is halved?

A. 2F

B. 0.5F

C. 4F

D. 0.25F

E None of above

IV. Two vehicles have a head on (but off center) collision as demonstrated in the picture. Which of the following quantities is changed by the collision?

A. Total mechanical energy.

B. Total linear momentum.

C. Total angular momentum.

D. Velocity of the center of mass of the two cars.

E. Total mass.

V. A cable is supporting a beam as shown in the figure. The tension in the cable is 200N. What is the corresponding torque over the hinge O ?

A. 172.1 Nm, clockwise

B. 172.1 Nm, anti-clockwise

C. 245.7 Nm, clockwise

D. 245.7 Nm, anti-clockwise

E. 300 Nm, anti-clockwise

VI. Consider the swinging motion of a pendulum. With respect to the figure, which of the following statement is not correct?

A. Potential energy at point A is maximum.

B. Velocity at point C is maximum.

C. Acceleration at point C is maximum.

D. Kinetic energy at point A is minimum.

E. The bob has the same speed at points B and D.

VII. If the length of a pendulum is increased by four times, the period will be

A. increased by four times.

B. decreased by four times.

C. halved.

D. doubled

E. remain the same.

VIII. Which of the following is not an electromagnetic wave?

A. X-ray

B. sound wave

C. light

D. radio wave

E. microwave

IX. WEKU broadcasts at a frequency of 88.9 MHz (1 MHz is 10⁶ Hz), what is the corresponding wavelength? Speed of sound is 330 ms^-1 and speed of light is 3 X 10⁸ ms^-1.

A. 2.67 X 10¹⁶ m

B. 3.71 X 10^-6 m

C. 266.7 m

D. 3.37 m

E. 2.93 X 10¹⁰m

X. Consider a pipe open at both ends, how many nodes are there in the first overtone (i.e. second harmonic)?

A. 1

B. 2

C. 3

D. 4

E. Depends on the length of the pipe.

2. (25 points)

A box is given a push so that it slides across the floor. How far will it go, given that the coefficient of kinetic friction is 0.32 and the push imparts an initial speed of 6.5 m/s?

3. (25 points)

(a) Calculate the translational and rotational speeds of a solid cylinder (radius 30cm and mass 40 kg), that rolls without slipping down a 20.0^o that is 10m long, when it reaches the bottom. Assume it started from rest. (b) What is the ratio of translational to rotational KE at the bottom? (Moment of inertia of a cylinder rotating about the central axis is MR², where M and R are mass and radius respectively.)

4. A 2 kg mass is moving on a frictionless, vertical track in the Earth's gravitation field as shown in the figure. At the highest point, its velocity is 5 ms^-1.

a. (10 points)

What will be the velocity when the object is at the lowest point of the track?

b. (15 points)

What is the normal force acting on the object when it is at the lowest point of the track? Give both magnitude and direction.

5. A 3 kg ball is approaching the stationary 2kg ball with a velocity of 4 m/s (see figure). After the collision, the 3kg continue to move in the original direction with a velocity of 1 m/s. There is no friction between the balls and the table top.

a. (13 points)

What is the speed of the 2 kg ball just after the collision?

b. (12 points)

At what distance from the bottom of the table will the 2 kg ball hit the floor if the table is 1 m high?

6. A figure skater is rotating at an initial rate of 0.5 revolution per second. She then reduces her moment of inertia from 4.6 kgm² to 0.77 kgm² by pulling her arms closer to her body.

a. (10 points)

What is the final angular speed of the skater after she pulls in her arms?

b. (10 points)

Calculate the initial and final rotational kinetic energy of the skater.

c. (5 points)

How much work the skater has to do in accomplishing this change?

7. A pendulum is formed by hanging a 0.5 kg bob at the end of a 1.5m long massless string. It is raised to make an angle of 5^o from the vertical and then released (from rest).

a. (12 points)

Calculate the period T, frequency f, and angular speed of the simple harmonic motion.