2. A 50 Kg box is sliding along a flat, horizontal plane, at a speed of 2 m/s. A
ID: 2032510 • Letter: 2
Question
2. A 50 Kg box is sliding along a flat, horizontal plane, at a speed of 2 m/s. A 200 N force is applied parallel to the ground, in a direction that speeds up the box, whereas a 100 N kinetic friction force is present between the box and the surface. (i) Calculate the work done by the 200 N force when the box has moved by 4 m. (ii) Calculate the work done by the kinetic friction force when the box has moved by 4 m. (iii) Calculate the work done by the normal force when the box has moved by 4 m. iv) Calculate the speed of the box when it has moved by 4 m.Explanation / Answer
Work done by 200N force = 200 × 4 = 800J
Work done by kinetic friction = 100×4 = 400J
Work done by normal force = 0
Change in K.E. = work done
1/2 mv^2 - 1/2 mu^2= 800 - 400 =400
1/2 ×50 × ( v^2 - u^2) =400
v^2 - 4 = 16
v= 4.47m/s
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