
Concept explainers
Consider the three connected objects shown in Figure P5.88. Assume first that the inclined plane is friction-less and that the system is in equilibrium. In terms of m, g, and θ, find (a) the mass M and (b) the tensions T, and T2. Now assume that the value of Af is double the value found in part (a). Find (c) the acceleration of each object and (d) the tensions T1 and T2. Next, assume that the coefficient of static friction between m and 2m and the inclined plane is m, and that the system is in equilibrium. Find (e) the maximum value of M and (0 the minimum value of M. (g) Compare the values of T2 when M has its minimum and maximum values.
(a)

The expression for the mass of M of the object.
Answer to Problem 5.88AP
The expression for the mass M is 3msinθ.
Explanation of Solution
The free body diagram of the three connected objects is shown in Figure below,
Figure (1)
From Figure (1), the equilibrium forces acts on the object of mass 2m in inclined plane is,
∑Fnet=T1−2mgsinθ
Here,
m is the mass of object.
g is the acceleration due to gravity.
θ is the angle of inclined plane.
T1 is the tension in the rope of mass 2m.
From the Newton’s second law of motion, the net force on the object of mass 2m is,
∑Fnet=(2m)a=2ma
Here,
a is the acceleration of the object.
Substitute T1−2mgsinθ for ∑Fnet in the above equation.
2ma=T1−2mgsinθ (1)
From Figure (1), the equilibrium forces act on the object of mass m in inclined plane is,
∑Fnet=T2−T1−mgsinθ
Here,
T2 is the tension in the rope of mass m.
From the Newton’s second law of motion, the net force on the object of mass m is,
∑Fnet=ma
Substitute T2−T1−mgsinθ for ∑Fnet in the above equation.
ma=T2−T1−mgsinθ (2)
Add the equation (1) with equation (2).
2ma+ma=T1−2mgsinθ+(T2−T1−mgsinθ)3ma=T2−3mgsinθT2=3m(a+gsinθ)
From Figure (1), the equilibrium forces act on the object of mass M is,
∑Fnet=Mg−T2
Here,
M is the mass of hanging object.
Substitute 3m(a+gsinθ) for T2 in the above equation.
∑Fnet=Mg−3m(a+gsinθ)
From the Newton’s second law of motion, the net force on the object of mass M is,
∑Fnet=Ma
Substitute Mg−3m(a+gsinθ) for ∑Fnet in the above equation.
Mg−3m(a+gsinθ)=MaM(g−a)=3m(a+gsinθ)M=3m(a+gsinθ)g−a
The system is in equilibrium so value of the acceleration is zero.
Substitute 0 for a in the above equation.
M=3m(0+gsinθ)g−0=3mgsinθg=3msinθ
Conclusion:
Therefore, the expression for the mass M is 3msinθ.
(b)

The expressions for tensions T1 and T2.
Answer to Problem 5.88AP
The expression for the tension T1 is 2mgsinθ and the expression for the tension T2 is 3mgsinθ.
Explanation of Solution
From part (a), the expression for the mass of M is,
M=3msinθ
From part (a), the equilibrium forces act on the object is,
∑Fnet=Mg−T2
The system is in equilibrium, the value of acceleration is zero so the net force acts on the system is also zero.
Substitute 0 for ∑Fnet in the above equation.
Mg−T2=0T2=Mg
Substitute 3msinθ for M in the above equation.
T2=(3msinθ)g=3mgsinθ
Thus, the expression for the tension T2 is 3mgsinθ.
From part (a), the equation (2) is,
ma=T2−T1−mgsinθ
Substitute 0 for a in the above equation.
m(0)=T2−T1−mgsinθT2−T1=mgsinθ
Substitute 3mgsinθ for T2 in the above equation.
3mgsinθ−T1=mgsinθT1=2mgsinθ
Thus, the expression for the tension T1 is 2mgsinθ.
Conclusion:
Therefore, the expression for the tension T1 is 2mgsinθ and the expression for the tension T2 is 3mgsinθ.
(c)

The acceleration of each object.
Answer to Problem 5.88AP
The acceleration of each object is gsinθ1+2sinθ.
Explanation of Solution
Given info: The value of mass M is double.
From part (a), the expression for the mass when it is double represents as,
M=2(3msinθ)=6msinθ
From part (a), the equation (1) is,
2ma=T1−2mgsinθ
Rearrange the above equation.
T1=2ma+2mgsinθ
From part (a), the equation (2) is,
ma=T2−T1−mgsinθ
Rearrange the above equation.
T2−T1=ma+mgsinθ
Substitute 2ma+2mgsinθ for T1 in the above equation.
T2−(2ma+2mgsinθ)=ma+mgsinθT2=3ma+3mgsinθ (3)
From Figure (1), the equilibrium forces act on the object of mass M is,
Ma=Mg−T2T2=M(g−a)
Substitute 6msinθ for M in the above equation.
T2=6msinθ(g−a) (4)
Subtract the equation (3) from equation (4).
T2−T2=6msinθ(g−a)−(3ma+3mgsinθ)6masinθ+3ma=6mgsinθ−3mgsinθa(1+2sinθ)=gsinθa=gsinθ1+2sinθ
Conclusion:
Therefore, the acceleration of each object is gsinθ1+2sinθ.
(d)

The expressions for tensions T1 and T2.
Answer to Problem 5.88AP
The expression for the tension T1 is 4mgsinθ(1+sinθ1+2sinθ) and the expression for the tension T2 is 6mgsinθ(1+sinθ1+2sinθ).
Explanation of Solution
From part (c), the expression for the acceleration is,
a=gsinθ1+2sinθ
From part (c), the equation for tension T1 is,
T1=2ma+2mgsinθ
Substitute gsinθ1+2sinθ for a in the above equation.
T1=2m(gsinθ1+2sinθ)+2mgsinθ=2mgsinθ(11+2sinθ+1)=2mgsinθ(2+2sinθ1+2sinθ)=4mgsinθ(1+sinθ1+2sinθ)
Thus, the expression for tension T1 is 4mgsinθ(1+sinθ1+2sinθ).
From part (c), the equation (3) is,
T2=3ma+3mgsinθ
Substitute gsinθ1+2sinθ for a in the above equation.
T2=3m(gsinθ1+2sinθ)+3mgsinθ=3mgsinθ(11+2sinθ+1)=3mgsinθ(1+1+2sinθ1+2sinθ)=6mgsinθ(1+sinθ1+2sinθ)
Thus, the expression for tension T2 is 6mgsinθ(1+sinθ1+2sinθ).
Conclusion:
Therefore, the expression for the tension T1 is 4mgsinθ(1+sinθ1+2sinθ) and the expression for the tension T2 is 6mgsinθ(1+sinθ1+2sinθ).
(e)

The maximum value of M.
Answer to Problem 5.88AP
The maximum value of M is 3m(sinθ+mscosθ).
Explanation of Solution
Given info: The coefficient of static friction between mass m, 2m and the inclined plane is ms.
The static friction forces on the masses m and 2m is shown in Figure below,
Figure (2)
From the Figure (2), the normal force on the object of mass 2m is,
n=2mgcosθ
The expression for the static friction force on the object of mass 2m and mass m is,
fs=msn (3)
Here,
ms is the coefficient of static friction.
n is the normal force.
Substitute 2mgcosθ for n in the above equation.
fs=ms(2mgcosθ)=2mmsgcosθ
From the Figure (1), the equilibrium forces acts on the object of mass 2m is,
2ma=T1−2mgsinθ−fs
Substitute 2mmsgcosθ for fs in the above equation.
2ma=T1−2mgsinθ−2mmsgcosθ (4)
Rearrange the above equation for T1.
T1=2ma+2mgsinθ+2mmsgcosθT1=2m(a+gsinθ+msgcosθ)
Substitute 0 for a in the above equation.
T1=2m(0+gsinθ+msgcosθ)=2mg(sinθ+mscosθ)
From the Figure (2), the normal force on the object of mass m is,
n=mgcosθ
Substitute mgcosθ for n in equation (3).
fs=msmgcosθ
From the Figure (1), the equilibrium forces acts on the object of mass m is,
ma=T2−T1−mgsinθ−fs
Substitute msmgcosθ for fs in the above equation.
ma=T2−T1−mgsinθ−msmgcosθ
Add equation (4) with the above equation.
2ma+ma=T1−2mgsinθ−2mmsgcosθ+T2−T1−mgsinθ−msmgcosθ3ma=−3mgsinθ−3mmsgcosθ+T2T2=3ma+3mgsinθ+3mmsgcosθT2=3m(a+gsinθ+msgcosθ)
Substitute 0 for a in the above equation.
T2=3m(0+gsinθ+msgcosθ)=3mg(sinθ+mscosθ)
The equilibrium forces on the block of mass M when mass is maximum represents as,
T2=Mmaxg
Substitute 3mg(sinθ+mscosθ) for T2 in the above equation.
3mg(sinθ+mscosθ)=MmaxgMmax=3m(sinθ+mscosθ)
Conclusion:
Therefore, the maximum value of M is 3m(sinθ+mscosθ).
(f)

The minimum value of M.
Answer to Problem 5.88AP
The minimum value of M is 3m(sinθ−mscosθ).
Explanation of Solution
From part (e), the expression of tension T2 for the minimum mass is,
T2=3mg(sinθ−mscosθ)
The equilibrium forces acts on block for minimum mass of M is,
T2=Mming
Substitute 3mg(sinθ−mscosθ) for T2 in the above equation.
3mg(sinθ−mscosθ)=MmingMmin=3m(sinθ−mscosθ)
Conclusion:
Therefore, the minimum value of M is 3m(sinθ−mscosθ).
(g)

The difference between the tension T2 for maximum and minimum mass.
Answer to Problem 5.88AP
The difference between the tension for maximum and minimum mass is 6msmgcosθ.
Explanation of Solution
From part (e), the expression for maximum mass is,
Mmax=3m(sinθ+mscosθ)
From part (f), the expression for the minimum mass is,
Mmin=3m(sinθ−mscosθ)
From part (e), the expression for the tension for maximum mass is,
T2,max=Mmaxg
From part (f), the expression for the tension for maximum mass is,
T2,min=Mming
Compare both the above equation.
T2,max−T2,min=Mmaxg−Mming
Substitute 3m(sinθ+mscosθ) for Mmax and 3m(sinθ−mscosθ) for Mmin in the above equation.
T2,max−T2,min=(3m(sinθ+mscosθ))g−(3m(sinθ−mscosθ))g=6msmgcosθ
Conclusion:
Therefore, the difference between the tension for maximum and minimum mass is 6msmgcosθ.
Want to see more full solutions like this?
Chapter 5 Solutions
Physics for Scientists and Engineers, Technology Update (No access codes included)
- Your RL circuit has a characteristic time constant of 19.5 ns, and a resistance of 4.60 MQ. (a) What is the inductance (in H) of the circuit? 0.00897 × H (b) What resistance (in MQ) should you use (instead of the 4.60 MQ resistor) to obtain a 1.00 ns time constant, perhaps needed for quick response in an oscilloscope? 8.97 * ΜΩarrow_forwardYour RL circuit has a characteristic time constant of 19.5 ns, and a resistance of 4.60 MQ. (a) What is the inductance (in H) of the circuit? H (b) What resistance (in MQ) should you use (instead of the 4.60 MQ resistor) to obtain a 1.00 ns time constant, perhaps needed for quick response in an oscilloscope? ΜΩarrow_forwardAt a distance of 0.212 cm from the center of a charged conducting sphere with radius 0.100cm, the electric field is 485 N/C . What is the electric field 0.598 cm from the center of the sphere? At a distance of 0.196 cmcm from the axis of a very long charged conducting cylinder with radius 0.100cm, the electric field is 485 N/C . What is the electric field 0.620 cm from the axis of the cylinder? At a distance of 0.202 cm from a large uniform sheet of charge, the electric field is 485 N/C . What is the electric field 1.21 cm from the sheet?arrow_forward
- A hollow, conducting sphere with an outer radius of 0.260 m and an inner radius of 0.200 m has a uniform surface charge density of +6.67 × 10−6 C/m2. A charge of -0.800 μC is now introduced into the cavity inside the sphere. What is the new charge density on the outside of the sphere? Calculate the strength of the electric field just outside the sphere. What is the electric flux through a spherical surface just inside the inner surface of the sphere?arrow_forwardA point charge of -3.00 μC is located in the center of a spherical cavity of radius 6.60 cm inside an insulating spherical charged solid. The charge density in the solid is 7.35 × 10−4 C/m3. Calculate the magnitude of the electric field inside the solid at a distance of 9.10 cm from the center of the cavity. Find the direction of this electric field.arrow_forwardAn infinitely long conducting cylindrical rod with a positive charge λ per unit length is surrounded by a conducting cylindrical shell (which is also infinitely long) with a charge per unit length of −2λ and radius r1, as shown in the figure. What is E(r), the radial component of the electric field between the rod and cylindrical shell as a function of the distance r from the axis of the cylindrical rod? Express your answer in terms of λ, r, and ϵ0, the permittivity of free space. What is σinner, the surface charge density (charge per unit area) on the inner surface of the conducting shell? What is σouterσouter, the surface charge density on the outside of the conducting shell? (Recall from the problem statement that the conducting shell has a total charge per unit length given by −2λ.) What is the radial component of the electric field, E(r), outside the shell?arrow_forward
- A very long conducting tube (hollow cylinder) has inner radius aa and outer radius b. It carries charge per unit length +α, where αα is a positive constant with units of C/m. A line of charge lies along the axis of the tube. The line of charge has charge per unit length +α. Calculate the electric field in terms of α and the distance r from the axis of the tube for r<a. Calculate the electric field in terms of α and the distance rr from the axis of the tube for a<r<b. Calculate the electric field in terms of αα and the distance r from the axis of the tube for r>b. What is the charge per unit length on the inner surface of the tube? What is the charge per unit length on the outer surface of the tube?arrow_forwardTwo small insulating spheres with radius 9.00×10−2 m are separated by a large center-to-center distance of 0.545 m . One sphere is negatively charged, with net charge -1.75 μC , and the other sphere is positively charged, with net charge 3.70 μC . The charge is uniformly distributed within the volume of each sphere. What is the magnitude E of the electric field midway between the spheres? Take the permittivity of free space to be ϵ0 = 8.85×10−12 C2/(N⋅m2) . What is the direction of the electric field midway between the spheres?arrow_forwardA conducting spherical shell with inner radius aa and outer radius bb has a positive point charge Q located at its center. The total charge on the shell is -3Q, and it is insulated from its surroundings. Derive the expression for the electric field magnitude in terms of the distance r from the center for the region r<a. Express your answer in terms of some or all of the variables Q, a, b, and appropriate constants. Derive the expression for the electric field magnitude in terms of the distance rr from the center for the region a<r<b. Derive the expression for the electric field magnitude in terms of the distance rr from the center for the region r>b. What is the surface charge density on the inner surface of the conducting shell? What is the surface charge density on the outer surface of the conducting shell?arrow_forward
- A small sphere with a mass of 3.00×10−3 g and carrying a charge of 4.80×10−8 C hangs from a thread near a very large, charged insulating sheet, as shown in the figure (Figure 1). The charge density on the sheet is −2.20×10−9 C/m2 . Find the angle of the thread.arrow_forwardA small conducting spherical shell with inner radius aa and outer radius bb is concentric with a larger conducting spherical shell with inner radius c and outer radius d (Figure 1). The inner shell has total charge +2q, and the outer shell has charge −2q. Calculate the magnitude of the electric field in terms of q and the distance rr from the common center of the two shells for r<a. Calculate the magnitude of the electric field for a<r<b. Calculate the magnitude of the electric field for b<r<c.arrow_forwardA cube has sides of length L = 0.800 m . It is placed with one corner at the origin as shown in the figure. The electric field is not uniform but is given by E→=αxi^+βzk^, where α=−3.90 and β= 7.10. What is the sum of the flux through the surface S5 and S6? What is the sum of the flux through the surface S2 and S4? Find the total electric charge inside the cube.arrow_forward
- Principles of Physics: A Calculus-Based TextPhysicsISBN:9781133104261Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers, Technology ...PhysicsISBN:9781305116399Author:Raymond A. Serway, John W. JewettPublisher:Cengage LearningPhysics for Scientists and Engineers: Foundations...PhysicsISBN:9781133939146Author:Katz, Debora M.Publisher:Cengage Learning
- Classical Dynamics of Particles and SystemsPhysicsISBN:9780534408961Author:Stephen T. Thornton, Jerry B. MarionPublisher:Cengage LearningUniversity Physics Volume 1PhysicsISBN:9781938168277Author:William Moebs, Samuel J. Ling, Jeff SannyPublisher:OpenStax - Rice UniversityPhysics for Scientists and Engineers with Modern ...PhysicsISBN:9781337553292Author:Raymond A. Serway, John W. JewettPublisher:Cengage Learning





