A block $$$B$$$ of mass $$$4 \mathrm{~kg}$$$ is pushed up a line of greatest slope of a smooth plane inclined at $$$30^{\circ}$$$ to the horizontal by a force applied to $$$B$$$, acting in the direction of motion of $$$B$$$. The block passes through points $$$P$$$ and $$$Q$$$ with speeds $$$12 \mathrm{~m} \mathrm{~s}^{-1}$$$ and $$$8 \mathrm{~m} \mathrm{~s}^{-1}$$$ respectively. $$$P$$$ and $$$Q$$$ are $$$10 \mathrm{~m}$$$ apart with $$$P$$$ below the level of $$$Q$$$ Hence find the work done by the force pushing the block up the slope as the block moves from $$$P$$$ to $$$Q$$$. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_s20_qp_43 Year：2020 Question No：5(b)

Answer:

PE gained $=4 g \times 10 \sin 30(=200)$
Total work done $=200-160$
Total work done $=40 \mathrm{~J}$

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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