Newton's Laws, Kinematics, and Friction

In summary, a student is pushing a 1.5 KG textbook initially at rest on a table with coefficients of static and kinetic friction of 0.25 and 0.20 respectively. The applied force is enough to overcome the force of friction and get the book to start moving, and is maintained for 1.5 seconds. The normal force is 14.7 N and the force of friction is -3.675 N. To determine the applied force, it must be equal to or greater than the force of friction.
  • #1
Mindflayer94
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Homework Statement



A student pushes horizontally northward on a 1.5 KG textbook initially at rest. The book is located 1.0m from the edge of a long table. the coefficient of static friction is 0.25, and the coefficient of kinect friction is 0.20. The applied force is just enough to get the book to start moving and is maintained for 1.5 seconds after the motion has begun.

B) Determine the Applied force (Fa) of the student to get the book moving

Homework Equations



Fnet = Fa + Ff
Fnet = mass* acceleration
|Fnormal| = |Fgravity| = |mass* g|

The Attempt at a Solution



I'm able to figure out that the normal force is 14.7 N, and that the force of friction is -3.675 N, (letting force against movement be negative). I'm just not sure how much force should be applied if it's "just enough to get the book to start moving"?

Any help would be greatly appreciated
:smile:
 
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  • #2
What they mean by "just enough to get the book moving" is a force essentially equal to overcome the force of friction for the static scenario. So the force of friction that you calculated already.
 

1. What are Newton's three laws of motion?

Newton's first law, also known as the law of inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. Newton's second law, also known as the law of acceleration, states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Newton's third law, also known as the law of action and reaction, states that for every action, there is an equal and opposite reaction.

2. How do you calculate the force of friction?

The force of friction can be calculated using the formula F = μN, where F is the force of friction, μ is the coefficient of friction, and N is the normal force. The coefficient of friction depends on the types of surfaces in contact and is typically given in tables or can be measured experimentally.

3. What is the difference between static and kinetic friction?

Static friction is the force that must be overcome to set an object in motion when it is at rest. It is typically greater than kinetic friction, which is the force that opposes the motion of an object that is already in motion. Static friction can vary in magnitude depending on the applied force, while kinetic friction remains constant.

4. What is the difference between speed and velocity?

Speed is a measure of how fast an object is moving, while velocity is a measure of how fast an object is moving in a specific direction. In other words, velocity takes into account the direction of an object's motion, while speed does not.

5. How does an object's mass affect its acceleration?

An object's mass is directly proportional to its acceleration, according to Newton's second law. This means that the greater the mass of an object, the more force is required to accelerate it at a certain rate. In other words, a heavier object will have a slower acceleration compared to a lighter object when the same force is applied.

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