Question 1

A ventilation fan has blades 0.25 m in radius rotating at 20 rpm.What is the tangential speed of each blade tip?

Accepted Answer

A)   0.02 m/s
B)   0.52 m/s
C)   5.0 m/s
D)   20 m/s B

Question 2

A 0.40-kg mass,attached to the end of a 0.75-m string,is whirled around in a circular horizontal path.If the maximum tension that the string can withstand is 450 N,then what maximum speed can the mass have if the string is not to break?

Accepted Answer

A)   370 m/s
B)   22 m/s
C)   19 m/s
D)   29 m/s D

Question 3

An asteroid is in orbit at 4 times the earth's distance from the Sun.What is its period of revolution?

Accepted Answer

A)   one fourth year
B)   4 years
C)   8 years
D)   16 years C

Question 4

A wheel is rotated about a horizontal axle at a constant angular speed.Next it is rotated in the opposite direction with the same angular speed.The acceleration at a point on the top of the wheel in the second case as compared to the acceleration in the first case:

Accepted Answer

A)   is in the same direction.
B)   is in the opposite direction.
C)   is upward.
D)   is tangential to the wheel.

Question 5

The escape speed from the surface of the Earth is 11.2 km/s.Estimate the escape speed for a spacecraft from the surface of the Moon.The Moon has a mass 1/81 that of Earth and a radius 0.25 that of Earth.

Accepted Answer

A)   2.5 km/s
B)   4.0 km/s
C)   5.6 km/s
D)   8.7 km/s

Question 6

The Earth's orbit is closest to the Sun in January and farthest from the Sun in July.When is the Earth moving the fastest in orbit?

Accepted Answer

A)   Neither January nor July since the orbital speed of the Earth is a constant.
B)   January
C)   July
D)   This occurs twice a year,in April and in October.

Question 7

A 0.30-m-radius automobile tire rotates how many rad after starting from rest and accelerating at a constant 2.0 rad/s2 over a 5.0-s interval?

Accepted Answer

A)   12.5 rad
B)   25 rad
C)   2.0 rad
D)   0.50 rad

Question 8

If a planet has 3 times the radius of the Earth,but has the same density as the Earth,what is the gravitational acceleration at the surface of the planet? (g = 9.8 m/s2)

Accepted Answer

A)   29.4 m/s2
B)   88.2 m/s2
C)   265 m/s2
D)   3.27 m/s2

Question 9

Suppose the gravitational potential energy for a mass at an altitude of one Earth radius is PE1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare?

Accepted Answer

A)  1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare? 
A)     
B)     
C)     
D)     but is not equal to   " class="answers-bank-image d-inline" rel="preload" >
B)  1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare? 
A)     
B)     
C)     
D)     but is not equal to   " class="answers-bank-image d-inline" rel="preload" >
C)  1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare? 
A)     
B)     
C)     
D)     but is not equal to   " class="answers-bank-image d-inline" rel="preload" >
D)  1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare? 
A)     
B)     
C)     
D)     but is not equal to   " class="answers-bank-image d-inline" rel="preload" > but is not equal to1 and at two Earth radii is PE2.How do the absolute values of these potential energies compare? 
A)     
B)     
C)     
D)     but is not equal to   " class="answers-bank-image d-inline" rel="preload" >

Question 10

An artificial Earth satellite in an elliptical orbit has its greatest centripetal acceleration when it is at what location?

Accepted Answer

A)   nearest the Earth
B)   farthest from the Earth
C)   between Earth and Moon
D)   between Earth and Sun

Question 11

Two points on a merry-go-round are located at distances from the center r1 and r2,where r1 2.While the merry-go-round is in the process of speeding up to operational speed,which of the following equations involving magnitudes of angular speed,angular acceleration,and tangential speed for these points is incorrect?

Accepted Answer

A)   ω1 = ω2
B)   α1 = α2
C)   vt1 = vt2
D)   All of the equations are correct.

Question 12

The acceleration due to gravity at the surface of Planet X is 10 m/s2.What is the acceleration due to gravity at an altitude of 3 000 km above the surface of this planet?

Accepted Answer

A)   10 m/s2
B)   8.0 m/s2
C)   4.4 m/s2
D)   More information is needed.

Question 13

An Earth satellite is orbiting at a distance from the Earth's surface equal to one Earth radius (4 000 miles).At this location,the acceleration due to gravity is what factor times the value of g at the Earth's surface?

Accepted Answer

A)   There is no acceleration since the satellite is in orbit.
B)   2
C)   1/2
D)   1/4

Question 14

At what location does an artificial Earth satellite in elliptical orbit have its greatest speed?

Accepted Answer

A)   nearest the Earth
B)   farthest from the Earth
C)   between Earth and Moon
D)   between Earth and Sun

Question 15

A Ferris wheel,rotating initially at an angular speed of 0.50 rad/s,accelerates over a 7.0-s interval at a rate of 0.040 rad/s2.What is its angular speed after this 7-s interval?

Accepted Answer

A)   0.20 rad/s
B)   0.30 rad/s
C)   0.46 rad/s
D)   0.78 rad/s

Question 16

A 0.150-m-radius grinding wheel,starting at rest,develops an angular speed of 12.0 rad/s in a time interval of 4.00 s.What is the centripetal acceleration of a point 0.100 m from the center when the wheel is moving at an angular speed of 12.0 rad/s?

Accepted Answer

A)   0.450 m/s2
B)   7.20 m/s2
C)   14.4 m/s2
D)   28.8 m/s2

Question 17

Consider a child who is swinging.As she reaches the lowest point in her swing:

Accepted Answer

A)   the tension in the rope is equal to her weight.
B)   the tension in the rope is equal to her mass times her acceleration.
C)   her acceleration is downward at 9.8 m/s2.
D)   none of the above.

Question 18

An asteroid in orbit about the sun has a linear speed of 4 km/s when at a distance of closest approach d from the sun.What is its linear speed when it is at its greatest distance from the sun,a distance 2 d?

Accepted Answer

A)   1 km/s
B)   2 km/s
C)   8 km/s
D)   16 km/s

Question 19

A fan blade,initially at rest,rotates with a constant acceleration of 0.025 rad/s2.What is the time interval required for it to reach a 4.2-rad displacement after starting from rest?

Accepted Answer

A)   1.8 s
B)   2.0 s
C)   16 s
D)   18 s

Question 20

Calculate the linear speed due to the Earth's rotation for a person at the equator of the Earth.The radius of the Earth is 6.40 × 106 m.

Accepted Answer

A)   74.0 m/s
B)   233 m/s
C)   465 m/s
D)   73.0 m/s

Exam 7: Rotational Motion and the Law of Gravity

A ventilation fan has blades 0.25 m in radius rotating at 20 rpm.What is the tangential speed of each blade tip?

A 0.40-kg mass,attached to the end of a 0.75-m string,is whirled around in a circular horizontal path.If the maximum tension that the string can withstand is 450 N,then what maximum speed can the mass have if the string is not to break?

An asteroid is in orbit at 4 times the earth's distance from the Sun.What is its period of revolution?

A wheel is rotated about a horizontal axle at a constant angular speed.Next it is rotated in the opposite direction with the same angular speed.The acceleration at a point on the top of the wheel in the second case as compared to the acceleration in the first case:

The escape speed from the surface of the Earth is 11.2 km/s.Estimate the escape speed for a spacecraft from the surface of the Moon.The Moon has a mass 1/81 that of Earth and a radius 0.25 that of Earth.

The Earth's orbit is closest to the Sun in January and farthest from the Sun in July.When is the Earth moving the fastest in orbit?

A 0.30-m-radius automobile tire rotates how many rad after starting from rest and accelerating at a constant 2.0 rad/s² over a 5.0-s interval?

If a planet has 3 times the radius of the Earth,but has the same density as the Earth,what is the gravitational acceleration at the surface of the planet? (g = 9.8 m/s²)

Suppose the gravitational potential energy for a mass at an altitude of one Earth radius is PE₁ and at two Earth radii is PE₂.How do the absolute values of these potential energies compare?

An artificial Earth satellite in an elliptical orbit has its greatest centripetal acceleration when it is at what location?

The acceleration due to gravity at the surface of Planet X is 10 m/s².What is the acceleration due to gravity at an altitude of 3 000 km above the surface of this planet?

An Earth satellite is orbiting at a distance from the Earth's surface equal to one Earth radius (4 000 miles) .At this location,the acceleration due to gravity is what factor times the value of g at the Earth's surface?

At what location does an artificial Earth satellite in elliptical orbit have its greatest speed?

A Ferris wheel,rotating initially at an angular speed of 0.50 rad/s,accelerates over a 7.0-s interval at a rate of 0.040 rad/s².What is its angular speed after this 7-s interval?

A 0.150-m-radius grinding wheel,starting at rest,develops an angular speed of 12.0 rad/s in a time interval of 4.00 s.What is the centripetal acceleration of a point 0.100 m from the center when the wheel is moving at an angular speed of 12.0 rad/s?

Consider a child who is swinging.As she reaches the lowest point in her swing:

An asteroid in orbit about the sun has a linear speed of 4 km/s when at a distance of closest approach d from the sun.What is its linear speed when it is at its greatest distance from the sun,a distance 2 d?

A fan blade,initially at rest,rotates with a constant acceleration of 0.025 rad/s².What is the time interval required for it to reach a 4.2-rad displacement after starting from rest?

Calculate the linear speed due to the Earth's rotation for a person at the equator of the Earth.The radius of the Earth is 6.40 × 10⁶ m.