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Matter & Interactions
Found in: Page 208

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Short Answer

In Figure 5.72 m1=12kgand m2=5kg . The kinetic coefficient of friction between m1 and the floor is 0.3 and that between m2 and the floor is 0.5. You push with a force of magnitude F=110N . (a) What is the acceleration of the center of mass? (b) What is the magnitude of the force that m1 exerts on m2?

(a) The acceleration of the center of mass is 2.95 m/s2.

(b) The magnitude of the force that m1exerts on m2 is 39.27N.

See the step by step solution

Step by Step Solution

Step 1: Identification of the given data

The given data can be listed below as:

  • The value of the first mass is,m1=12kg .
  • The value of the second mass is,m2=5kg .
  • The coefficient of friction between the floor and the first mass is μ1=0.3.
  • The coefficient of friction between the floor and the second mass is μ2=0.5 .
  • The force required to push the masses are F=110N .

Step 2: Significance of the coefficient of friction

The coefficient of friction is described as the ratio between the friction and the normal force. However, the coefficient of friction mainly depends on surface roughness and nature of the material used.

Step 3: (a) Determination of the acceleration of the center of mass

The equation of the net force is expressed as:

Fnet=F-(μ1m1g+μ2m2g)

Here,Fnet is the net force, F is the force required to push the masses, μ1is the coefficient of friction between the floor and the first mass,m1 is the mass of the first mass, g is the acceleration due to gravity, μ2 is the coefficient of friction between the floor and the second mass and m2 is the mass of the second mass.

Substitute the values in the above equation.

Fnet=110 N-0.3×12 kg×9.8 m/s2+0.5×5 kg×9.8 m/s2 =110 N-35.28 kg.m/s2+24.5 kg.m/s2 =110 N-59.78kg.m/s2×1N1 kg.m/s2 =50.22 N

The equation of the acceleration of the center of mass is expressed as:

a=Fnetm1+m2

Here, a is the acceleration of the center of mass,Fnet is the net force, m1 is the mass of the first mass and m2is the mass of the second mass.

Substitute the values in the above equation.

a=50.22 N12 kg+5 kg =50.22 N17 kg =2.95N/kg =2.95N/kg×kg.m/s2/1N =2.95 m/s2

Thus, the acceleration of the center of mass is 2.95 m/s2.

Step 4: (b) Determination of the magnitude of the force

The equation of the magnitude of the force that the first mass exerts on the second mass is expressed as:

F1=m2a+μ2m2g

Here, F1 is the magnitude of the force that the first mass exerts on the second mass, a is the acceleration of the center of mass, g is the acceleration due to gravity, μ2 is the coefficient of friction between the floor and the second mass and m2 is the mass of the second mass.

Substitute the values in the above equation.

F1=5 kg2.95 m/s2+0.55 kg9.8 m/s2 =14.77 kg.m/s2+24.5 kg.m/s2 =39.27 kg.m/s2×1N1kg.m/s2 =39.27 N

Thus, the magnitude of the force that m1 exerts on m2 is39.27N .

Most popular questions for Physics Textbooks

(a) Many communication satellites are placed in a circular orbit around the Earth at a radius where the period (the time to go around the Earth once) is \(24\;{\rm{h}}\). If the satellite is above some point on the equator, it stays above that point as the Earth rotates, so that as viewed from the rotating Earth the satellite appears to be motionless. That is why you see dish antennas pointing at a fixed point in space. Calculate the radius of the orbit of such a "synchronous" satellite. Explain your calculation in detail.

(b) Electromagnetic radiation including light and radio waves travels at a speed of \(3 \times {10^8}\;{\rm{m}}/{\rm{s}}\). If a phone call is routed through a synchronous satellite to someone not very far from you on the ground, what is the minimum delay between saying something and getting a response? Explain. Include in your explanation a diagram of the situation.

(c) Some human-made satellites are placed in "near-Earth" orbit, just high enough to be above almost all of the atmosphere. Calculate how long it takes for such a satellite to go around the Earth once, and explain any approximations you make.

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(e) When the first two astronauts landed on the Moon, a third astronaut remained in an orbiter in circular orbit near the Moon's surface. During half of every complete orbit, the orbiter was behind the Moon and out of radio contact with the Earth. On each orbit, how long was the time when radio contact was lost?

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