# Homework Help: Projectile trajectory (True/False)

1. Sep 7, 2009

### sonutulsiani

1. The problem statement, all variables and given/known data

The figure represents the trajectory of a projectile going from A to F. Air resistance is negligible.

http://bcs.whfreeman.com/WebPub/Physics/tiplerphysics6e_bridge/question_bank_images/3-24.png?81

2. Relevant equations

For all the following sentences choose True or False:

1. At point F the speed is the greatest?

2. At point C the velocity vector has only an horizontal component?

3. At points B and D the velocities are the same?

4. At point C the acceleration is zero?

5. The time it takes the particle to get from point A to point C is greater than the time it takes it to get from point C to point F?

6. The horizontal component of the velocity at point E is the same as the horizontal component of the velocity at point A?

7. Let →vD , →vE be the velocity vectors at points D and E respectively.
The vector (→vE) − (→vD) is directed vertically downwards?

3. The attempt at a solution

I got as

1. True
2. False
3. True
4. False
5. True
6. False
7. I didn't understand it.

Now I don't know if these answers are correct or not.

Last edited: Sep 7, 2009
2. Sep 7, 2009

### Quincy

If we could see the diagram, that would be really helpful.

3. Sep 7, 2009

4. Sep 7, 2009

### Quincy

For #5, why do you say it is true?
As for #7, I'm not sure what the question is asking.

5. Sep 7, 2009

### sonutulsiani

Are the rest of the questions correct? except 5?
7 is like, the arrows are on top of v, so it's like velocity vector

6. Sep 7, 2009

### Quincy

Yes
I know, that's not what I don't get.

7. Sep 7, 2009

### sonutulsiani

So 5 is false, but then why is it false? Does it take the same time?

8. Sep 7, 2009

### Quincy

Of course, it's symmetrical. Think of it as a parabola on a graph where time is on the x axis and meters are on the y axis. It takes the same time for it to get from A to C as it does for it to get from C to F.

9. Sep 7, 2009

### drizzle

for 7# what do you know about horizontal component of particle’s velocity that follows Projectile trajectory?

10. Sep 7, 2009

### sonutulsiani

I wrote here all the information I had.

11. Sep 7, 2009

### Quincy

There's also implied information. Since it's a projectile, you know that the x-components of the velocity vectors at all points are the same since there's no acceleration in the horizontal direction.

12. Sep 7, 2009

### drizzle

I know, this is not about your Q but more [as a general role] you should know this, as Quincy said the horizontal component of the velocity is always constant, now knowing that the velocity at E> the velocity at D [you know why?] what do you think the answer is true/false?

13. Sep 7, 2009

### Jebus_Chris

Here is what I got.

14. Sep 9, 2009

### sonutulsiani

That was awesome brother. I understood each and every question. Thanks for providing the reasons also. :)
Peace.