Example 2: a) A desk has a mass of 68.75 kilograms. If the coefficient of static friction between the desk and the floor is 1.1, what force must be used to move the desk from rest?
b) Once the desk above is in motion, what force must be used to keep it moving at a constant velocity if the coefficient of kinetic friction is 0.73?
xample 2: a) A desk has a mass of 68.75 kilograms. If the coefficient of static friction between the desk and the floor is 1.1, what force must be used to move the desk from rest?
b) Once the desk above is in motion, what force must be used to keep it moving at a constant velocity if the coefficient of kinetic friction is 0.73?
To answer both of these questions, we need to understand the concept of friction and how it relates to motion.
Friction is a force that opposes the relative motion between two surfaces in contact. There are two types of friction: static friction and kinetic friction. Static friction acts on an object at rest and prevents it from moving, while kinetic friction acts on an object in motion.
a) To calculate the force required to move the desk from rest, we need to determine the maximum static friction force. The equation to calculate the maximum static friction force is:
Maximum static friction force = coefficient of static friction x normal force
The normal force is the force exerted by the surface on the object and is equal to the weight of the object in most cases. The equation to calculate the weight of an object is:
Weight = mass x acceleration due to gravity
In this case, the mass of the desk is given as 68.75 kilograms. The acceleration due to gravity is approximately 9.8 m/s^2.
So, the weight of the desk is:
Weight = 68.75 kg x 9.8 m/s^2
Once we have the weight, we can calculate the maximum static friction force using the given coefficient of static friction.
Maximum static friction force = 1.1 x weight
b) Once the desk is already in motion, the force required to keep it moving at a constant velocity is given by the equation:
Force = coefficient of kinetic friction x normal force
Similar to part a, we need to calculate the normal force by finding the weight of the desk using the mass and the acceleration due to gravity. Then, we can calculate the force using the given coefficient of kinetic friction.
I hope this explanation helps you understand how to solve these types of problems!