Question

In: Physics

A basket full of apples weighing 40.0 N (the force of gravity) rests on a horizontal...

A basket full of apples weighing 40.0 N (the force of gravity) rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.40 and the coefficient of kinetic friction is 0.20.

A: If no horizontal force is applied to the basket and the basket is at rest, how large is the friction force exerted on the box?

B: A farmer applies a horizontal force of 6.0 N to the basket when the basket is initially at rest. What is the magnitude of the friction force on the basket?

C: What is the smallest horizontal force that will start the basket in motion if it is originally at rest?

D: What is the smallest horizontal force the farmer must apply to keep the basket moving at constant velocity once it has started to move?

E: If the farmer exerts a horizontal force of 18.0 Non the basket, what is the magnitude of the friction force ?

F: If the farmer applies a horizontal force of 18.0 N, what is the basket's acceleration?

Solutions

Expert Solution

A) Since no horizontal force is applied to the basket, the basket is already in Equilibrium in that direction.The friction force acting on it will be zero.

B) Since 6 N horizontal force is applied to the basket, the friction force tries to counter it. The maximum static friction force is given by: . As 6 N < 16 N, the static friction force can balance it.

The friction force acting on the basket is 6 N.

C) The smallest horizontal force to move the basket is equal to the maximum static friction force which opposes the movement. Thus, the smallest horizontal force to move the basket is 16 N.

D) Once the basket is moving, kinetic friction force oposes its motion which is given by:

Thus, the farmer must apply minimum of 8 N to keep the basket moving.

E) 18 N is greater than the maximum static friction force acting on the basket which is 16 N. Thus, the basket moves and the friction force acting on it is equal to the kinetic friction force which is 8 N.

F) Using Newton's second law in the horizontal direction,  

The basket's acceleration is 2.4525 m/s2.


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