While riding a bicycle,if we stop pedalling,why does the bicycle begin to slow down?

Explain with a suitable example whether or not the force of friction always acts opposite to the direction of motion.

$A$ body of mass $500 \, g$ is at rest on a frictionless surface. Calculate the distance travelled by it in $10 \, s$ when acted upon by a force of $10^{-2} \, N$. (in $, m$)

An athlete runs some distance before taking a long jump,because

$A$ book of mass $2 \, kg$ is sliding with a constant velocity of $4 \, m s^{-1}$ on a frictionless horizontal table. What is the force required to keep the object moving with the same velocity (in $, N$)?

$(a)$ State the law of conservation of momentum.
$(b)$ Mention two factors which determine the momentum of a body.
$(c)$ Prove the law of conservation of momentum with clear explanation,diagram and equation.