# Can a body continue in a Straight line if force is not parallel to velocity?

A body was travelling in a Straight line with initial velocity v. A non-constant force (both in terms of magnitude and direction) starts acting on the body at an angle theta with the direction of velocity at that instant (such that theta is always greater than 0° and less than 90°).

Is it possible that the body continues to travel in the straight line as it was travelling initially?

[Theta may change from instant to instant]

• The perpendicular component of the force will change the direction of motion. – Yashas Apr 17 '17 at 9:28
• It's possible if there is a second force ... ;) – Sanya Apr 17 '17 at 10:01
• @Sanya : "a" single force , not more than one. – Madhuchhanda Mandal Apr 17 '17 at 10:15
• Are there other forces acting on the body as well? – fibonatic Apr 17 '17 at 10:30

As long as $0° \geq \theta \geq 90°$ for the angle the force acts at, the force will never be fully parallel to the body, and will therefore always have some component of acceleration which changes the direction of the velocity.