A 48 kg box is being pushed a distance of 7.0 m across the floor by a force whose magnitude is 155 N. The force is parallel to the displacement of the box. The coefficient of kinetic friction is 0.25. Determine the work done on the box by each of the four forces that act on the box. Be sure to include the proper plus or minus sign for the work done by each force.
applied force___1085____J
frictional force __________J
normal force ____0_____J
gravity ____0____J
I filled in the answers that I know already please help me find the "frictional force" Thank you
2007-05-03 22:02:13 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Frictional force is the normal force times the coef. of friction pointing the opposite direction of motion. Normal Force points up from the ground and is equal in magnitude to mass(box) times acceleration due to gravity.
2007-05-03 22:07:21 · answer #1 · answered by Anonymous · 0⤊ 0⤋
The First Guy's SI unit is wrong work = J not N.
Anyway
F(friction) = Force acting (weight here)* coefficient of friction*cosA * 7
= F * s= 48*10*.25*7;
= Therefore work done by friction is - 840 J
Even though work is a scalar work is defined as FS cos A
if A > 90 then it is negative and frictional force is always negative cause it opposes and never suceeds
Thus Answer = -840 J
2007-05-03 22:11:27 · answer #2 · answered by akshayrangasai 2 · 0⤊ 0⤋
Work = Force * distance
As the box, never moves vertically, then the work done by the normal force and gravity equals zero.
friction force = u * N, where u is the coefficient of friction and N is the normal reaction, which is equal to the weight in this instance.
f = u*m*g = 0.25*48*9.8 = 117.6 N
Work done by f = 117.6 * 7 = 823.2 J
Work is a scalar. Therefore it does not have a direction ( and an associated positive or negative number).
2007-05-03 22:10:09 · answer #3 · answered by dudara 4 · 0⤊ 0⤋
Work done by applied force is correct : +1085 J
Work done by frictional force force is:48x9.8x.25x7= -823.2 J
frictional force always opposes the motion so it has to be negative. Also negative energy means moving body will transfer its energy to the floor.
The work done by net force would be 1085 - 823.2 = 261.8 J
This will be the change in kinetic energy of the body.
2007-05-04 02:56:58 · answer #4 · answered by Let'slearntothink 7 · 0⤊ 0⤋