Question

force applied on an object may change its speed how

Answer 1

whenthe we applied force on any body by increasing speed because extra force will also help in increasing speed

Answer 2

HEY MATE HERE IS YOUR ANSWER
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According to Newton's law of inertia,
"EVERY BODY CONTINUES IN ITS STATE OF REST
OR OF UNIFORM MOTION UNLESS TREATED
WITH AN EXTERNAL UNBALANCED FORCE"

Therefore a body need a force to change its velocity(not speed) and remains in uniform motion unless did so