Kinetic frictions, pulleys, and Newton's third law

In summary, the problem involves two blocks, A and B, connected by a frictionless pulley. Block A experiences a kinetic friction force of 5.7N while moving. The masses of A and B are 2.7kg and 3.7kg, respectively. We need to find the magnitude of the acceleration of the blocks and the tension in the string. To solve this, we can use the equations ƩFx=ma(x), ƩFy=ma(y), a(x)= ƩFx/m, Fnet(a)=Ft=Fk, Fnet(b)=Fg-Ft, and Ft(b)=Ft(a). After setting up the equations, we can solve for the
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Homework Statement


Block A and B are connected by a string passing over an essentially frictionless pulley. (Block A is on a horizontal plane, while block B is suspended in the air) When the blocks are moving block A experiences a force of kinetic friction of magnitude 5.7N. If mA= 2.7kg and mB= 3.7kg calculate the magnitude of:
(a) The acceleration of the blocks
(b) The tension in the string


Homework Equations


ƩFx=ma(x)
ƩFy=ma(y)
a(x)= ƩFx/m
Fnet(a)= Ft=Fk
Fnet(b)= Fg-Ft
Ft(b)=Ft(a)



The Attempt at a Solution


ƩF(a)= Ft-Fk
= Ft- 5.7N
ƩF(b)= Fg-Ft
= mg-Ft
=(3.7kg)(9.8N)-Ft
=36.26N-Ft
 
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1. What is kinetic friction?

Kinetic friction is a type of friction that occurs between two surfaces that are in motion relative to each other. It is caused by the microscopic irregularities on the surfaces that come into contact and resist the motion.

2. How do pulleys work?

Pulleys are simple machines that consist of a wheel with a groove around its circumference and a rope or cable that runs along the groove. When a force is applied to one end of the rope, the wheel turns and the other end of the rope moves in the desired direction.

3. What is Newton's third law of motion?

Newton's third law of motion states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.

4. How does Newton's third law apply to pulleys?

In pulley systems, the forces acting on the pulley and the rope are always equal and opposite according to Newton's third law. This allows for the transfer of force and motion in different directions, making pulleys useful for lifting heavy objects.

5. How does friction affect the motion of objects?

Friction can either increase or decrease the speed of an object depending on the direction of the applied force. In the case of kinetic friction, it always acts in the opposite direction of the motion, causing a decrease in speed. This is why it is important to consider friction when calculating the motion of objects.

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