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Physics 10 Kinematics Rotational Motion Formative assessment.doc
Section 5.1 Uniform Circular Motion
Section 5.2 Centripetal Acceleration
¦ 1. A ball moves with a constant speed of 4 m/s around a circle of radius 0.25 m. What is the period of the motion?
(a) 0.1 s (c) 0.7 s (e) 2 s
(b) 0.4 s (d) 1 s
¦ 2. The second hand on a watch has a length of 4.50 mm and makes one revolution in 60.00 s. What is the speed of the end of the second hand as it moves in uniform circular motion?
(a) 9.42 ґ 10-4 m/s (c) 5.34 ґ 10-3 m/s (e) 2.36 ґ 10-5 m/s
(b) 2.67 ґ 10-3 m/s (d) 4.71 ґ 10-4 m/s
¦ 3. Approximately one billion years ago, the Moon orbited the Earth much closer than it does today. The radius of the orbit was only 24 400 km. Today, the radius is 385 000 km. The orbital period was only 23 400 s. The present period is 2.36 ґ 106 s. Assume that the orbit of the Moon is circular. Calculate the ratio of the speed of the Moon in its ancient orbit to the speed that it has today.
(a) 15.8 (c) 10.2 (e) 6.39
(b) 12.8 (d) 7.15
Ј 4. A racecar is traveling at constant speed around a circular track. What happens to the centripetal acceleration of the car if the speed is doubled?
(a) The centripetal acceleration remains the same.
(b) The centripetal acceleration increases by a factor of 2.
(c) The centripetal acceleration increases by a factor of 4.
(d) The centripetal acceleration is decreased by a factor of one-half.
(e) The centripetal acceleration is decreased by a factor of one-fourth
¦ 5. A ball is whirled on the end of a string in a horizontal circle of radius R at constant speed v.
Complete the following statement: The centripetal acceleration of the ball can be increased by a factor of 4 by
(a) keeping the speed fixed and increasing the radius by a factor of 4.
(b) keeping the radius fixed and increasing the speed by a factor of 4.
(c) keeping the radius fixed and increasing the period by a factor of 4.
(d) keeping the radius fixed and decreasing the period by a factor of 4.
(e) keeping the speed fixed and decreasing the radius by a factor of 4.
ў 6. A rock is whirled on the end of a string in a horizontal circle of radius R with a constant period T.
If the radius of the circle is reduced to R/2, while the period remains T, what happens to the centripetal acceleration of the rock?
(a) The centripetal acceleration remains the same.
(b) The centripetal acceleration increases by a factor of 2.
(c) The centripetal acceleration increases by a factor of 4.
(d) The centripetal acceleration decreases by a factor of 2.
(e) The centripetal acceleration decreases by a factor of 4.
¦ 7. A car traveling at 20 m/s rounds a curve so that its centripetal acceleration is 5 m/s2.
What is the radius of the curve?
(a) 4 m (c) 80 m (e) 640 m
(b) 8 m (d) 160 m
¦ 8. A satellite is placed in a circular orbit to observe the surface of Mars from an altitude of 144 km. The equatorial radius of Mars is 3397 km. If the speed of the satellite is 3480 m/s, what is the magnitude of the centripetal acceleration of the satellite?
(a) 2.17 m/s2 (c) 2.99 m/s2 (e) 4.05 m/s2
(b) 2.60 m/s2 (d) 3.42 m/s2
Questions 9 and 10 pertain to the following situation:
One of the world’s largest Ferris wheels, the Cosmo Clock 21 with a radius of 50.0 m is located in Yokohama City, Japan. Each of the sixty gondolas on the wheel takes 1.00 minute to complete one revolution when it is running at full speed. Note: Ignore gravitational effects.
¦ 9. What is the uniform speed of a gondola when the Ferris wheel is running at full speed?
(a) 314 m/s (c) 10.5 m/s (e) 5.24 m/s
(b) 1.67 m/s (d) 18.6 m/s
¦ 10. What is the centripetal acceleration of the gondola when the Ferris wheel is running at full speed?
(a) 0.548 m/s2 (c) 2.21 m/s2 (e) 6.28 m/s2
(b) 6.91 m/s2 (d) 0.732 m/s2
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