Object moving at constant speed - manually increase speed?

Physics
#1

Hi,

I have an object moving at a constant speed. To achieve that I use zero gravity, a body with 100% bounce and a force applied to that physics body.

[lua]

physics.setGravity(0, 0)

…

physics.addBody( ball.object, { density=0, friction=0, bounce=1, radius=ball.size } )

ball.object:applyForce( x, y, ball.object.x, ball.object.y )

[/lua]

After collision the speed stays the same and that’s great. But, I want to manually increase speed from time to time.

How can I do this? Can I get the current X and Y force applied to an moving object? Something like this?

[lua]

ball.object:applyForce( ball.object.currentForceX, ball.object.currentForceY, ball.object.x, ball.object.y )

[/lua]

Daniel

#2

@Daniel,

Hi.  I answered this question (page down a bit) with a video and a link to code which should help: http://forums.coronalabs.com/topic/51384-apply-impulse-applies-floating-point-force-instead-of-constant/

PS - Read my answers in the prior part of the post too, where I talk about how applyForce() works.

#3

Thank you. Solved by changing applyForce to applyLinearImpulse:

[lua]

local x = getRandomDirection()

local y = getRandomDirection()

ball.object:applyLinearImpulse( x * ball.object.mass, y * ball.object.mass, ball.object.x, ball.object.y )

[/lua]

I can now increase speed using another impulse:

[lua]

local vx, vy = collision.ball.object:getLinearVelocity()

log:log("Current velocity: ", vx, vy)

local impulseX = (vx * collision.ball.increaseSpeedFactor / collision.ball.multiplyScore) * collision.ball.object.mass

local impulseY = (vy * collision.ball.increaseSpeedFactor / collision.ball.multiplyScore ) * collision.ball.object.mass

collision.ball.object:applyLinearImpulse( impulseX, impulseY, collision.ball.object.x, collision.ball.object.y )

log:log(“Linear impulse applied to increase velocity”, impulseX, impulseY)[/lua]

Daniel

#4

@Daniel,

Hi.  I answered this question (page down a bit) with a video and a link to code which should help: http://forums.coronalabs.com/topic/51384-apply-impulse-applies-floating-point-force-instead-of-constant/

PS - Read my answers in the prior part of the post too, where I talk about how applyForce() works.

#5

Thank you. Solved by changing applyForce to applyLinearImpulse:

[lua]

local x = getRandomDirection()

local y = getRandomDirection()

ball.object:applyLinearImpulse( x * ball.object.mass, y * ball.object.mass, ball.object.x, ball.object.y )

[/lua]

I can now increase speed using another impulse:

[lua]

local vx, vy = collision.ball.object:getLinearVelocity()

log:log("Current velocity: ", vx, vy)

local impulseX = (vx * collision.ball.increaseSpeedFactor / collision.ball.multiplyScore) * collision.ball.object.mass

local impulseY = (vy * collision.ball.increaseSpeedFactor / collision.ball.multiplyScore ) * collision.ball.object.mass

collision.ball.object:applyLinearImpulse( impulseX, impulseY, collision.ball.object.x, collision.ball.object.y )

log:log(“Linear impulse applied to increase velocity”, impulseX, impulseY)[/lua]

Daniel