# Physics

Two uniform solid spheres have the same mass of 3 kg, but one has a radius of 0.25 m while the other has a radius of 0.8 m. Each can rotate about an axis through its center.

(a) What is the magnitude τ of the torque required to bring the smaller sphere from rest to an angular speed of 300 rad/s in 15 s?
N·m

(b) What is the magnitude F of the force that must be applied tangentially at the sphere's equator to provide that torque?
N

(c) What is the corresponding value of τ for the larger sphere?
N·m

(d) What is the corresponding value of F for the larger sphere?
N

1. 👍 0
2. 👎 0
3. 👁 573
asked by Josh
1. I sphere = (2/5) mR^2
see http://hyperphysics.phy-astr.gsu.edu/hbase/isph.html

I1 = (2/5)3 (.25)^2 = .075
alpha = 300/15 = 20 radians/second^2
Torque = I alpha = .075*20 = 1.5 Nm

F1 = torque/R = 1.5/.25 = 6 N

now big sphere
I2 = (2/5)3 (.8)^2 = .768
torque = I alpha = .768*20 = 15.36 Nm
F2 = 15.36/.8 = 19.2 N

1. 👍 0
2. 👎 0
posted by Damon

## Similar Questions

1. ### physics

A solid lead sphere of radius 10 m (about 66 ft across!) has a mass of about 57 million kg. If two of these spheres are floating in deep space with their centers 20 m apart, the gravitational attraction between the spheres is only

asked by anonymous on March 11, 2014
2. ### College Physics

A bowling ball (mass = 4.4 kg, radius = 0.11 m) and a billiard ball (mass = 0.35 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the

asked by Anonymous on March 14, 2012
3. ### Physics

Two spheres are cut from a certain uniform rock. One has radius 3.54 cm. The mass of the other is 3 times greater. Find its radius.

asked by Student on January 29, 2017
4. ### Physics

Two spheres are cut from a certain uniform rock.One has radius 4.50 cm.The mass of the other is five times greater. Find its radius.

asked by Amy on September 24, 2011
5. ### physics

5. A bowling ball (mass = 7.2 kg, radius = 0.13 m) and a billiard ball (mass = 0.45 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the

asked by sam on June 27, 2013
6. ### physics

A bowling ball (mass = 7.2 kg, radius = 0.12 m) and a billiard ball (mass = 0.31 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the

asked by cody on February 10, 2012
7. ### Physics

A bowling ball (mass = 7.2 kg, radius = 0.14 m) and a billiard ball (mass = 0.40 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the

asked by Donald on October 3, 2012
8. ### Physics

Three uniform spheres are located at the corners of an equilateral triangle. Each side of the triangle has a length of 1.60 m. Two of the spheres have a mass of 2.20 kg each. The third sphere (mass unknown) is released from rest.

asked by NHS on September 17, 2007
9. ### Physics

Three uniform spheres are located at the corners of an equilateral triangle. Each side of the triangle has a length of 3.10 m. Two of the spheres have a mass of 3.20 kg each. The third sphere (mass unknown) is released from rest.

asked by Anonymous on October 10, 2012
10. ### Advance Physics

Three uniform spheres are located at the corners of an equilateral triangle. Each side of the triangle has a length of 1.48 m. Two of the spheres have a mass of 2.18 kg each. The third sphere (mass unknown) is released from rest.

asked by A51AN on March 6, 2008

More Similar Questions