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Course:

Question

Introduction to Physics

1

2

Date: 2021-12-13

3

Total

Score

Name

Constant Table:

0 =8.8510-12C2N–1m-2 ; R=8.315J-mol-1K-1; 0= 4π10-7NA-2; h = 6.6310-34Js;

e = 1.60210-19C; G =6.6710-11Nm2-kg-2; me=9.1110-31kg; g=9.8 m/s2;

1. Fill in blanks with correct answer: (Total 30 marks with every blank 6 marks)

(1) The size of the momentum of a 30 g arrow with a speed of 12 m/s is

.

(2) A force is applied to a wheel with diameter of 20 cm. The radial component is 7 N and

the tangential component is 14 N. The torque is

.

(3) The simple harmonic wave on a string is y = 0.02 cos[ (5 x − 200t )] meter. Its

frequency f is

.

(4) An amount of heat equal to 2500 J is added to a system, and 1800 J of work is done on

the system. The change in internal energy of the system is

.

(5) To accelerate a 1000 kg car from 20 m/s to 30 m/s, the work required is

.

2. Choose one correct answer among the following choices: (Total 30 marks with every

question 6 marks)

(1) Which one of the following statements about torque is not correct? (

(A) The torque causes angular acceleration.

(B) The torque depends on the magnitude and direction of the force.

(C) The torque depends on the location of the axis.

(D) The torque does not depend on the point where the force acts.

)

(2) Two systems are in thermal equilibrium. The two systems are at the same (

(A) pressure

(B) volume

(C) temperature

(D) internal energy

)

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(3) For the ideal gas, isothermal process means (

(A) Temperature is constant.

(B) Pressure is constant.

(C) Volume is constant.

(D) No heat flows into or out of the system.

)

(4) Which one of the following statements about action force and reaction force is not

correct? (

)

(A) Action force and reaction force always occur in pairs

(B) Action force and reaction force must be of the same type

(C) Action force and reaction force act on the same object

(D) Action force and reaction force appear and disappear at the same time

(5) Which force is not conservative force? (

(A) gravity

(B) restoring force

(C) frictional force

(D) electrostatic force

)

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3. Calculate the Following Problems: (2 problems, total 40 marks)

(1) (20 marks) A uniform rod of mass M and length L can pivot freely (Ignoring friction)

about a hinge attached to the case of a large machine shown in figure 1. The rod is held

horizontally and then released. At the moment of release, determine (I) the angular

acceleration of the rod, and (II) the linear acceleration of the tip of the rod. Assuming the

force of gravity acts at the center of mass of the rod. The moment of inertia of a uniform

1

rod pivoted about its end is I= ML2.

3

Figure 1

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(2) (20 marks)

A ball of mass m=2.6 kg, starting from rest y1, falls a vertical distance h=0.55 m before

striking a vertical coiled spring, and it compresses an amount Y=0.15 m at the position of

y3 seen in figure 2. Determine the spring constant of the spring. Assume the spring has

negligible mass, and measure all distances from the point where the ball first touches the

uncompressed spring y2.

Figure 2

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