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Question:
A block of mass $2 \mathrm{~kg}$ placed on a long frictionless horizontal table is pulled horizontally by a constant force $F$. It is found to move $10 \mathrm{~m}$ in the first two seconds. Find the magnitude of $F$.
Solution:
$F=m a$
From law of kinematics,
$x-x_{0}=u t+\frac{1}{2} a t^{2}$
$10=\frac{a 2^{2}}{2}$
$(u=0)$
$a=5 m / s^{2}$
$F=m a=2 \times 5=10 \mathrm{~N}$
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