## Translational Motion Content Review Video

mcat5122018
Posts: 17
Joined: Sat Mar 03, 2018 3:33 pm

### Translational Motion Content Review Video

Hi,

In the translational content review video, Clara states one thing we need to understand is linear and exponential graphs. Can you please explain what we need to understand for each of those types of graph?

For the attached pictures, can you explain what the correct answer are and why they are correct? I was a bit confused by the explanations. For one of them it stated "north of west would be closer due to north than west" and that did not make sense to me.

Physics is definitely one of the most difficult topics for me to understand.

Attachments
Physica Quiz Question 2.png
Physics Quiz Question.png
NS_Tutor_Andrew
Posts: 520
Joined: Mon May 23, 2016 1:47 pm

### Re: Translational Motion Content Review Video

Hi mcat5122018 --

For linear vs. exponential graphs, the main idea is to be able to recognize them and understand what they're saying conceptually -- i.e. that for a linear graph, moving a certain "distance" on the x-axis will mean moving a consistent "distance" on the y-axis, whereas for exponential and logarithmic graphs, a certain delta X does not mean a consistent delta Y. The idea here is basically that when you learn that a certain relationship in physics is linear or exponential, you should also be able to visualize what that means mathematically, and vice-versa.

For the question about west/north, I've attached a diagram illustrating what the explanation means by saying that "53° north of west would be closer to due north than west" (but I used an angle of 60° to make the math easier). Basically, "53° north of west" means that there will be a 53° angle between the vector and the west axis, while 53° west of north means that there will be a 53° angle between the vector and the north axis.

The question about the blocks is a little difficult to visualize intuitively because we're likely to imagine that the external opposing force would stop the blocks simultaneously. But let's consider what the equation tells us. We know that we can use the equation F = ma to model what happens when the external opposing force stops the masses. The Q stem tells us that F is constant, but we know that the mass of the objects differ. Therefore, for F to be the same for both masses despite their different masses, they must each have different values for the acceleration term. Acceleration is change in velocity divided by change in time. The change in the velocity term must be the same, though, because the Q tells us that their initial velocity is the same, and the final velocity for both is zero. This means that the only way the acceleration term can be different is for the change in time to be different, which is why the time required to bring Block 1 to a stop will differ from that required for Block 2.

Hope this helps!
Attachments
Screen Shot 2018-03-19 at 9.50.10 AM.png