Lab #7

One complete revolution corresponds to 360 degrees which corresponds to ____________. A. 2*Pi radians B. Pi radians C. 2 radians D. Pi/4 radians E. Pi/2 radians

A. 2*Pi radians

Why is it necessary to measure from the center of the shaft to the pointer? A. Because the outer part of the shaft rotates too. B. It is not necessary.

A. Because the outer part of the shaft rotates too

Given w = angular speed in rad/sec and R = radius of the circular path of an object moving in uniform circular motion with period T and frequency f. The linear speed v of the object is expressed as A. v = R*w B. v = w/R C. v = R/w D. v = R*w^2 E. v = 2*Pi*f

A. v = R*w

Given w = 62.8 rad/s for an object moving in uniform circular motion, what is the period of the motion in seconds? A.0.100 s B. 0.1 s C. 100 s D. 10 s E. 6.28 s

A.0.100 s

A 0.500 kg mass is attached to the end of a 1.50 m cord . The ball is whirled in a horizontal circle with a radius equal to the length of the string. If the cord can withstand a maximum tension of 50.0 N, what is the maximum speed the ball can have before the cord breaks? A. 12.25 m/s B. 12.2 m/s C. 150. m/s D. 15 m/s E. 0.75 m/s

B. 12.2 m/s

Given w = 62.8 rad/s and R = 0.50 m for a 0.50 kg object moving in uniform circular motion, what is the centripetal force causing the object to accelerate? A. 500 N B. 990 N C. 246 N D. 985 N E. 15.7 N

B. 990 N

If a centripetal acceleration is experienced or measured, it necessarily follows that: A. The instantaneous velocity vector is in the same direction as the measured acceleration B. An unbalanced force acts in the direction of the acceleration C. A centrifugal force acts in the direction of the acceleration D. A reactive centrifugal acceleration exists E. A balanced force acts in the direction of the acceleration

B. An unbalanced force acts in the direction of the acceleration

Why do you find the percent difference between the two centripetal force values and not the percent error? A. B and C B. Both values were calculated, therefore neither one was an accepted value C. Because there was no error in the experiment D. There was such a big difference between the two values E. A and B

B. Both values were calculated, therefore neither one was an accepted value

How did you find the period of the rotated mass? A. By finding the time for ten revolutions and multiplying by ten. B. By finding the time for ten revolutions and dividing by ten. C. By timing one revolution. D. By finding the frequency and then inverting it. E. We didn't.

B. By finding the time for ten revolutions and dividing by ten.

How do you determine the weight required to cause the pointer and index to coincide? A. By measuring the speed of rotation B. By using hanging masses, because W = mg C. It is impossible to determine the weight D. It is printed on the rotating mass E. It is always zero

B. By using hanging masses, because W = mg

What is the term used to describe a fictitious force that seems to be directed outward along the radius of a circle, acting on the rotating object of interest, in uniform circular motion, if the observer is located in the system of reference that moves with the object? A. Force of friction B. Centrifugal force C. Centripetal force D. Reaction to centripetal force E. Force of gravity

B. Centrifugal force

If an object is at rest it remains at rest; or if the object is moving it keeps moving with constant velocity unless acted upon by a net external force. This is a statement of Newton's A. Zeroth Law B. First Law C. Law of Universal Gravitation D. Second Law E. Third Law

B. First Law

As the pointer is moved farther out, how does the centripetal force change? Why? A. It decreases because the linear speed of the mass increases. B. It increases because the linear speed of the mass increases. C. It stays the same. D. It decreases because the linear speed of the mass decreases. E. It increases because the linear speed of the mass decreases.

B. It increases because the linear speed of the mass increases.

The natural unit of angular displacement, defined as the angle subtended by an arc length equal to one radius, is called the: A. Minute of arc (1/60 of 1/360 of a complete revolution) B. Radian C. Mil (which is 1/6400 of a complete revolution) D. Degree (which is 1/360 of a complete revolution) E. Second of arc (1/60 of 1/60 of 1/360 of a complete revolution)

B. Radian

A centripetal force of 318 N acts on mass m = 2 kg moving in uniform circular motion of radius R = 1 m with w = 12.6 rad/s. No useful work is done because: A. All of the work is dissipated to friction B. The centripetal force is balanced by centrifugal force C. Centripetal force acts perpendicular to the instantaneous displacement of the revolving mass D. Centripetal force is fictitious E. The tangential component of the centripetal force equals the radial component

B. The centripetal force is balanced by centrifugal force

If a centripetal acceleration is experienced or measured, it necessarily follows that: A. A reactive centrifugal acceleration exists B. The direction of the acceleration is in the direction of the change in velocity vector C. A balanced force acts in the direction of the acceleration D. The instantaneous velocity vector is in the same direction as the measured acceleration E. A centrifugal force acts in the direction of the acceleration

B. The direction of the acceleration is in the direction of the change in velocity vector

In the apparatus used for this experiment, the centripetal force of a stretched spring balances the inertia due to the rotating mass. A. False B. True

B. True

Given w = 62.8 rad/s and R = 0.50 m for an object moving in uniform circular motion with period. In m/s what is the linear speed of the motion? A. 12.3 m/s B. 62 m/s C. 31 m/s D. 6.28 m/s E. 31.4 m/s

C. 31 m/s

Uniform circular motion means the: A. Rate of change of the velocity vector opposes the acceleration B. Magnitude of the velocity vector increases at a constant rate C. Speed of the revolving mass is constant D. Velocity of the revolving mass is constant E. Direction of the acceleration is constant

C. Speed of the revolving mass is constant

Given w = 62.8 rad/s for an object moving in uniform circular motion. In hertz what is the frequency of the motion? A. 6.2 Hz B. 20 Hz C. 6.28 Hz D. 10.0 Hz E. Hz

D. 10.0 Hz

In m/s what is the linear speed of a point at the equator on the surface of the earth? Assume the radius of the earth to be 6.40x10^3 kilometers. HINT: the earth rotates 2*Pi radians in 24.0 hours OR one rotation per day OR 360 degrees in 24.0 hours. A. 585 m/s B. .465 m/s C. 707 m/s D. 465 m/s E. 465.4 m/s

D. 465 m/s

A car of mass 2000.0 kg is traveling at a constant speed of 85 m/s in a curve with radius 15 m. What is the centripetal acceleration? A. 5.70 m/s^2 B. 482 m/s^2 C. 5.7 m/s^2 D. 480 m/s^2 E. 1.7x10^5 m/s^2

D. 480 m/s^2

At what angular speed would the earth have to rotate in order for objects at the equator to have no weight. Assume the radius of the earth to be 6.40E03 kilometers. HINT: weight = mg; g = A. 9.81 m/s^2. B. 0.071 rad/s C. 0.0012 rad/s D. 6125 rad/s E. 0.00124 rad/s F. 1.53x10^-6 rad/s

D. 6125 rad/s

Centripetal literally means ____________ while centrifugal is defined as ______________. A. Radially outward; radially inward B. Center-fleeing; center-seeking C. Eccentric (off-center); intrinsic D. Center-seeking; center-fleeing E. Central; radial

D. Center-seeking; center-fleeing

The tendency of an object to oppose a change in its state of relative rest or constant velocity and measured by its mass is called: A. Centripetal force B. Momentum C. Acceleration D. Inertia E. Centrifugal force

D. Inertia

Why was it necessary to rotate the shaft at a constant speed? A. So that there will not be any centrifugal acceleration B. So that there will not be any centripetal acceleration C. So that you wouldn't get bored. D. So that the centripetal force is always exactly equal to the centrifugal force. E. So that the mass wouldn't fly off the end

D. So that the centripetal force is always exactly equal to the centrifugal force.

In rad/s what is the angular speed the earth? Assume the radius of the earth to be 6.40x10^3 km and the period of rotation to be 24.0 hours. A. 465 rad/s B. 5.43x10^5 rad/s C. 7.272x10^-5 rad/s D. 2.62x10^-1 rad/s E. 7.27x10^-5 rad/s

E. 7.27x10^-5 rad/s

Given w = angular speed in rad/sec and R = radius of the circular path of an object moving in uniform circular motion with period T and frequency f. Which of the following is NOT an expression of centripetal force? A. F = (4PI^2)*(f^2)*R*m B. F = (mv^2)/R C. F = ((4Pi^2)*R*m)/T^2 D. F = mRw^2 E. F = m*2*Pi*w

E. F = m*2*Pi*w

What was a source of error in your experiment? A. All of the above B. both values were experimental C. not wearing safety glasses D. friction E. Not keeping the pointer pointing at the center of the index

E. Not keeping the pointer pointing at the center of the index

Centripetal force is directed radially inward for an object traveling in a circle. What is applying the centripetal force? A. Friction of the rotating mass against the sides B. Rotating mass times the angular velocity squared divided by radius C. You are applying the force by adjusting the rotator speed D. The rotating object itself E. The tension in the spring

E. The tension in the spring