Ice pond with no friction -- how to get across?

[lola1227]

Homework Statement

You find yourself trapped in the middle of the icy pond. The ice is perfectly frictionless! Fortunately, you have a bucket of old hockey pucks with you (which you don't mind losing). How can you use these pucks to get you to shore? (use all of newton's 3 laws in your answer)

Relevant Equations

Newtons Law's
1: A body in motion will stay in motion and a body at rest will stay in rest unless acted upon by an external force
2: The force acting on an object is equal to the mass of the object times its acceleration (F=ma)
3: For every action there is an opposite and equal reaction

Would we use the mass of the bucket and pucks to get a higher acceleration?

I don't understand the use of the pucks in this question?

How would the three laws relate to this?

 

[haruspex]

Would we use the mass of the bucket and pucks to get a higher acceleration?

Yes, but how?
How much acceleration do you need? (Newton 1)

 

[lola1227]

Yes, but how?
How much acceleration do you need? (Newton 1)

we don't need a specific acceleration, mass or anything. no numbers are needed for this question. All that is needed is how we would use the hockey pucks and the laws to get to shore.

 

[haruspex]

we don't need a specific acceleration, mass or anything. no numbers are needed for this question. All that is needed is how we would use the hockey pucks and the laws to get to shore.

I am not asking for numbers, just a qualitative statement.

 

[phinds]

The ice is perfectly frictionless!

That's the key statement. Why?

 

[lola1227]

That's the key statement. Why?

You get moved back with the force? So, the action of throwing forward gives and equal and opposite reaction of you moving backwards (or vice versa) which leads you closer to shore. This correlates with Newton's third law?
And there's no friction acting in the way?

 

[lola1227]

I am not asking for numbers, just a qualitative statement.

Enough acceleration to get mass moving? F=ma so, enough acceleration for the force to be great enough to move?

 

[phinds]

You get moved back with the force? So, the action of throwing forward gives and equal and opposite reaction of you moving backwards (or vice versa) which leads you closer to shore. This correlates with Newton's third law?
And there's no friction acting in the way?

Right. Since there is no friction, it takes almost no force at all to get you there, it's just that more force will get you there faster. SO ... throw one puck and you get there in a while, throw them all one after another and you get there a lot more quickly.

 

[jbriggs444]

Enough acceleration to get mass moving?

How much is that? Is there a minimum?

 

[lola1227]

Right. Since there is no friction, it takes almost no force at all to get you there, it's just that more force will get you there faster. SO ... throw one puck and you get there in a while, throw them all one after another and you get there a lot more quickly.

Oh ok! Then the first law, since you're already moving with the force, since you're in motion you would stay in motion? and when starting off you're still so you would remain still, until you start throwing the hockey pucks (an external/unbalanced force) which is how Newtons first law comes into place?

 

[lola1227]

How much is that? Is there a minimum?

Force has to be greater than 0? Because when we do f/m=a the force has to bigger than 0 to get an acceleration?

 

[haruspex]

Force has to be greater than 0? Because when we do f/m=a the force has to bigger than 0 to get an acceleration?

Yes. If the ice is completely frictionless you only need to get some movement.

 

[hmmm27]

No need to waste pucks andor buckets : turn head one way, inhale ; turn the other way, exhale.

 

[mfb]

It's largely irrelevant in which direction you face when inhaling as the air will stream in from all directions. Only exhaling will produce thrust. Exhaling is a really inefficient propulsion method, however, and clearly the problem statement asks about using hockey pucks.