## lovekiller 2 years ago A soccer ball is kicked in space, where we assume there is no friction or other forces acting on the ball, at 13 m/s. How much force is needed to keep the ball moving?

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1. Outkast3r09

$S=\frac{1}{2}at^2+vt+s_0$ $S=\frac{1}{2}at^2+vt$ $V=at+V_0$ assuming the ball was sitting in space at rest $V=at=13$ $\frac{13}{a}=t$

None. since there is no other forces impeding its movement, and since it is moving with uniform velocity, then it will, by Newton's first law, continue to move.

3. Outkast3r09

I thought the question asked what was the force upon the ball -.-

yes. the question asks what is the force on the ball that keeps it moving.

5. TimSmit

In the case of the force required to get the ball to 13 m/s, it also depends on how long you exert the force and the mass of the ball. If you apply 10000N but only for a microsecond, you won't gain much velocity. The relation between force and acceleration is $F = m*a = m * \frac{ \Delta v }{ \Delta t }$ Then, to gain a speed of 13 m/s, the relation is: $13 = \frac{ F * \Delta t }{ m }$

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