Astudent moves a box of books down the hall
by pulling on a rope attached to the box. the
student pulls with a force of 174 n at an angle
of 35.0 above the horizontal. the box has a
mass of 25.1 kg, and μk between the box and
the floor is 0.25.
the acceleration of gravity is 9.81 m/s2 .
find the acceleration of the box.
answer in units of m/s2

  Working formula for both problems is Newton's 2nd Law of Motion, i.e., 

F = ma 

where 

F = net force acting on a body 
m = mass of the body 
a = acceleration of the body 

For Problem #1 --- 

The working formula is 

F = 174(cos Θ) - µmg = ma 

where 

Θ = angle at which force is pulling = 35 deg 
µ = 0.25
g = acceleration due to gravity = 9.8 m/sec^2 (constant) 

and all other terms have been previously defined. 

Substituting appropriate values, 

174(cos 35) - 0.25(25.1)(9.8) = 25.1a 

Solving for "a" 

a = 8.71 m/sec^2 

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The correct answer is  "c".  it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings. 

Sorry i don’t know what to do