10TH GRADE PRACTICE
Physics Problems: Dynamics, Grade 10
Newton's laws and fundamental forces.
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Problem statements
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Problem #35
Dynamics: Newton's lawsWhat force must be applied to a lead block of volume so that it moves with acceleration ? How much will a dynamometer spring stretch? , if you hang this block from it?
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The same block hangs on the spring, so it is stretched by gravity.
Answer
Problem #36
Dynamics: Newton's lawsForce imparts mass to a body acceleration , and a body of mass - acceleration . What acceleration will this force impart to a body of mass ?
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The force is the same, so we express the masses through it.
Answer
Problem #37
Dynamics: forces and balanceOn a sled with a load of mass horizontal force acts . With what acceleration does the sled move if the coefficient of friction is equal to ?
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Answer
Problem #38
Dynamics: Newton's lawsForce imparts acceleration to the body . What force will impart acceleration to this body? ?
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In short: F_1/F_2 = a_1/a_2, whence F_2 = F_1 a_2 / a_1.
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Problem #39
Dynamics: Newton's lawsWith what acceleration does a rocket with a mass of , if the engine thrust is equal to ?
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Upward is the force of gravity, downward is the force of gravity.
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Problem #40
Dynamics: forces and balanceWith what force do the Earth and the Sun attract? Accept , , . What diameter would a steel cable hold the Earth at its breaking point? ?
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Problem #41
Dynamics: forces and balanceBody mass moved across the table, the friction coefficient is equal to . What force must be applied for uniform motion and for accelerated motion? ? What will happen with the forces and ?
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For uniform movement, traction balances friction.
The body will not move: a static friction force of 5 N arises.
Answer
Problem #42
Dynamics: forces and balanceMasses of weights are suspended from the ends of a weightless lever and . Distance from fulcrum to smaller load . Determine the length of the lever.
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Rule of moments about the fulcrum.
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Problem #43
Dynamics: forces and balanceBeam with mass lies on two supports. One support is located at the end of the beam, the other at a distance of a quarter of the length from the other end. With what force does the beam press on the supports?
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We take the moments relative to the first support; the center of gravity is in the middle of the beam.
According to Newton's third law, the beam presses on the supports with the same forces.
Answer
Problem #44
Dynamics: Newton's lawsMan of mass presses on the floor of the elevator with force . Determine the magnitude and direction of acceleration of the elevator.
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A person presses less than he weighs, which means the elevator accelerates down or slows down when ascending.
According to Newton's third law.
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Problem #45
Dynamics: forces and balanceUnder the influence of horizontal force block of mass moving with acceleration . Determine the coefficient of friction.
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In one line: mu = (F - ma)/(mg).
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Problem #46
Dynamics: forces and balanceBody mass falls from a height for . Determine the force of air resistance. Accept .
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The actual acceleration is less than g, which means that the air is slowing down the body.
Answer
Problem #47
Dynamics: Newton's lawsForce imparts acceleration to the body . What force will impart acceleration to this body? ?
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The mass of the body is the same, so the force is proportional to the acceleration.
Answer
Problem #48
Dynamics: forces and balanceBody mass moves along a horizontal surface under the influence of force . The friction coefficient is equal to . What is the formal result of calculating acceleration using a sliding model?
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A negative value is a formal result: the applied force is not enough to move the body.
Answer
Problem #49
Dynamics: forces and balanceWhat should be the coefficient of friction so that a motorcyclist can pass a turn with a radius at speed ?
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During a turn, friction plays the role of centripetal force.
The mass is reduced - the result does not depend on it.
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Problem #50
Dynamics: Newton's lawsMan of mass presses on the floor of the elevator with force . Determine the acceleration of the elevator.
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Problem #51
Dynamics: forces and balanceAt what speed should a cyclist travel so that at the top point of the bridge the radius of curvature push on the bridge with a force half that of gravity?
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At the top point of the bridge, the force of gravity and the reaction of the support are in opposite directions.
Answer
Problem #52
Dynamics: forces and balanceWhat is the force holding the car's mass at a turn with a radius at speed ? What is the maximum speed at the coefficient of friction ?
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Problem #53
Dynamics: Newton's lawsThe elevator is moving with acceleration . The weight presses on the floor with force . What two masses of a load are possible depending on the direction of acceleration?
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The sign of acceleration depends on where the elevator is accelerating.
Acceleration is directed upward - overload, more weight.
Acceleration is directed downwards - partial weightlessness.
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Problem #62
Dynamics: forces and balanceBall mass hanging on a long thread . He is taken to and let go. Determine the thread tension at the lowest point.
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The ball is retracted 90°, so it descends exactly the length of the thread.
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