The mass disappeared out of view so I could not continue to apply force F on it.
To Nicepants - as soon as I do not apply a force on the mass, it stops accelerating and continues at constant speed on the frictionless surface. It is like a rocket - apply force and it accelerates. Apply no force - it stops accelerating.
Another example is two masses m (total 2 m) adjacent to one another on a frictionless surface. If force F is applied to the first mass, it applies F on the second mass and both masses accelerate at a =F/(2m) . The second mass evidently applies force -F on the first mass in this joint acceleration (as per Newton's third law). When force F is removed the two masses glide away at constant speed with no forces acting on them.
Now a static problem - the Pizza Tower. It is standing on ground and the top drops down on it. WOSH. And then there is an impact. BANG. Nothing really happens and particularly no global collapse ensues. The static Pizza Tower remains standing. The top rests on top.
What happened at BANG kan be treated as a static problem. Energy/forces are applied during a certain (short) time - they were not there before BANG so we freeze the time and look what happens just after BANG and what happens. OK, there might be some deformations to the Pizza Tower and the top that dropped (a dynamic event) but we only look at the end result of the BANG. Maybe one part failed so there will be another BANG when something drops, but we can study it too, statically.
Then we have this problem with the 1 kg mass that a force F = 1 N acts on so that it accelerates with a = 1 m/s² in a positive direction. So after 1 second it is moving at speed v = 1 m/s in the positive direction. At this time another force F2 = 11 N is applied to it in the opposite direction. As F - F2 = 10 N a total force F3 = 10 N is now applied to the mass and it accelerates with a = 10 m/s² in the other F2 direction - the negative direction. The speed 1 m/s in the F positive direction is then quickly slowed down and the mass accelerates in the F2 negative direction. A simple, dynamic problem.
Luckily the Pizza Tower remains standing and the 3 pizzas dropping on it does not accelerate through it ... at any time.
To Nicepants - as soon as I do not apply a force on the mass, it stops accelerating and continues at constant speed on the frictionless surface. It is like a rocket - apply force and it accelerates. Apply no force - it stops accelerating.
Another example is two masses m (total 2 m) adjacent to one another on a frictionless surface. If force F is applied to the first mass, it applies F on the second mass and both masses accelerate at a =F/(2m) . The second mass evidently applies force -F on the first mass in this joint acceleration (as per Newton's third law). When force F is removed the two masses glide away at constant speed with no forces acting on them.
Now a static problem - the Pizza Tower. It is standing on ground and the top drops down on it. WOSH. And then there is an impact. BANG. Nothing really happens and particularly no global collapse ensues. The static Pizza Tower remains standing. The top rests on top.
What happened at BANG kan be treated as a static problem. Energy/forces are applied during a certain (short) time - they were not there before BANG so we freeze the time and look what happens just after BANG and what happens. OK, there might be some deformations to the Pizza Tower and the top that dropped (a dynamic event) but we only look at the end result of the BANG. Maybe one part failed so there will be another BANG when something drops, but we can study it too, statically.
Then we have this problem with the 1 kg mass that a force F = 1 N acts on so that it accelerates with a = 1 m/s² in a positive direction. So after 1 second it is moving at speed v = 1 m/s in the positive direction. At this time another force F2 = 11 N is applied to it in the opposite direction. As F - F2 = 10 N a total force F3 = 10 N is now applied to the mass and it accelerates with a = 10 m/s² in the other F2 direction - the negative direction. The speed 1 m/s in the F positive direction is then quickly slowed down and the mass accelerates in the F2 negative direction. A simple, dynamic problem.
Luckily the Pizza Tower remains standing and the 3 pizzas dropping on it does not accelerate through it ... at any time.