A box of mass $$$5 \mathrm{~kg}$$$ is pulled at a constant speed a distance of $$$15 \mathrm{~m}$$$ up a rough plane inclined at an angle of $$$20^{\circ}$$$ to the horizontal. The box moves along a line of greatest slope against a frictional force of $$$40 \mathrm{~N}$$$. The force pulling the box is parallel to the line of greatest slope. Find the work done by the pulling force. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w20_qp_43 Year：2020 Question No：2(c)

Answer:

$W D=40 \times 15+5 \times 10 \times 15 \sin 20=857 \mathrm{~J}$

Knowledge points:

4.5.3 understand and use the relationship between the change in energy of a system and the work done by the external forces, and use in appropriate cases the principle of conservation of energy Including cases where the motion may not be linear (e.g. a child on a smooth curved ‘slide’), where only overall energy changes need to be considered.

Answer:

Knowledge points:

Solution:

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