A force that is doing work on a ball when that ball is falling through the air.
1 answer:
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1) In an uniformly accelerated motion, the acceleration is given by:
where
is the final speed, 
is the initial speed, and 
is the time interval between the initial and final point of the motion.
Using the data of the problem:
, 
, and the time 
, the acceleration is
where the negative sign means that the hockey puck is decelerating.
2) The frictional force F between the puck and ice is responsible for the deceleration of the puck, and for second Newton's law this force is equal to the product between the mass of the puck m and the acceleration:
(1)
The frictional force can also be written as
(2)
where
is the coefficient of kinetic friction, and where the negative sign is due to the fact that the frictional force acts against the direction of motion of the puck. By equilizing (1) and (2) we can find the value of this coefficient:
where
Using the data of the problem:
where the negative sign means that the hockey puck is decelerating.
2) The frictional force F between the puck and ice is responsible for the deceleration of the puck, and for second Newton's law this force is equal to the product between the mass of the puck m and the acceleration:
The frictional force can also be written as
where