12. Until the time of Galileo and Newton, people believed...

12. Until the time of Galileo and Newton, people believed that a constant force is required to produce a constant speed. Do your observations confirm or reject this notion? 13. What happens to the speed as you proceed farther and farther along the measured distance? 14. What happens to the rate of increase in speed – the acceleration – as you proceed farther and farther along the measured distance? 15. When the force is the same, how does the acceleration depend upon the mass? 16. When the mass of the skater is the same, how does the acceleration depend upon the force? Trial | Distance (m) | Force (N) | Time (s) | Speed (m/s) ---|---|---|---|--- 1 | 5m | 10N | 12s | 0.4m/s | 10m | 10N | 23s | 0.4m/s | 15m | 10N | 21s | 0.7m/s 2 | 5m | 15N | 8s | 0.7m/s | 10m | 15N | 20s | 0.5m/s | 15m | 15N | 18s | 0.9m/s 3 | 5m | 20N | 9s | 0.6m/s | 10m | 20N | 14s | 0.7m/s | 15m | 20N | 16s | 0.9m/s

Transcript

00:01 Okay, so this question, we're supposed to use newton's first law of motion, which states that an object in motion will only change its motion if there's a net force acting on it.

00:14 So that newton's first law of motion gives us that f force is equal to m .a.

00:20 So if the mass of an object is constant and it has a certain acceleration, like its motion is changing, it's not a constant velocity, it's not stationary.

00:29 So if the acceleration is not zero, then the force, there will be a net force acting on the object that is not zero.

00:37 So if we were take a look at some example of a velocity graph, and we see that the velocity changes over time, this slope is going to be equal to the acceleration here.

00:50 So whatever the slope is, that's acceleration.

00:51 So if the velocity is changing at a constant rate, then there's a constant acceleration, and that means that the force on an object is constant.

01:00 Now, if the velocity were to say, like curve like this or something like this, that means that the acceleration is not constant, it's changing at the same time as the velocity is changing.

01:13 So that means that there's a net force on it that's either increasing or decreasing.

01:16 So in this case, if the velocity is positive in this direction, the acceleration is pulling, is causing the velocity to decrease.

01:25 And so therefore the net force on this object is decreasing.

01:30 From the positive and it's going towards a negative.

01:33 So it's going to start increasing in the negative direction.

01:36 Now, we can use this knowledge to answer this question.

01:39 And so for questions a and b, it asks us, when is the net force on the object increasing or decreasing? now, we notice in the graph that the velocity is never curved.

01:49 It's always a constant.

01:50 And so that means that the net force is never actively increasing or decreasing in any certain time period.

01:55 So that means that for these a and b, that these are non -applicable, there's no answers to these...

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