1) In our first example we will consider a very simple application of Newton’s s

Question

1) In our first example we will consider a very simple application of Newton’s second law. A worker with spikes on his shoes pulls with a constant horizontal force of magnitude 20 N on a box with mass 40 kg resting on the flat, frictionless surface of a frozen lake. What is the acceleration of the box?

Answer = 0.5 m/s2

If the box starts from rest and the worker pulls with a force of 40 N , what is the speed of the box after it has been pulled a distance of 0.36 m ?

2) A heavy mirror that has a width of 1 m is to be hung on a wall as shown in the figure below. The mirror weighs 700 N , and the wire used to hang it will break if the tension exceeds 700 N(breaking strength). What is the shortest length of wire L that can be used to hang the mirror without the wire breaking? (Ignore any friction forces between the mirror and the wall.)

Explanation / Answer

you have asked two different question.As per guidelines i can only answer one.Please raise different question for another one.

summation of Fx=20N

F=ma(force=mass *accleration)

now accleration=F/m

=20/40

=0.5m/s^2

work=E

and E=1/2mv^2

Work=Fd

so Fd=1/2mv^2

v^2=0.5*m/Fd

=0.5*40/40*0.36

v^2=1.38

v=1.17m/sec

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