Solving a Physics Problem: Forces, Acceleration, and Work

AI Thread Summary
The discussion focuses on solving a physics problem involving a child pulling a sled with a dog, analyzing forces, acceleration, and work. The normal force is calculated as the difference between the child's force and the frictional force, resulting in 8.563 N. The acceleration of the system is determined to be 0.428 m/s² based on the normal force and total mass. The work done by the child over a distance of 7 meters is calculated to be approximately 59.94 J. The term "normal" refers to the perpendicular force exerted by a surface on an object resting on it.
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A child pulls a 15kg sled containing a 5kg dog along a straight path on a horizontal surface. He exerts a force of a 55N on the sled at an angle of 20 degree above the horizontal. The coefficient of friction between the sled and the surface is 0.22 .
Find:a) normal force of the surface on the system , b) the acceleration of system, c) the work done by the child as the system move 7m.
This is how i approach them

a)normal force = Force of the child exert - Force of friction
55cos20 - .22( (15+5)9.8 ) = 8.563 N

b)normal force= ma
8.563N = ( 15+5 )a
a=.428m/s^2

c)W=Fd W=8.563(7)= 59.94J

give me suggest if I am make a mistake
 
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What do you understand "normal" to mean when talking about surfaces?
 

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