Gravity is negative in those three questions. There was a miniature y axis depiction given in the top right corner of the diagram, indicating that an upward arrow would mean positive , while downward would mean negative. Gravity, always acting downwards here, is negative 9.8 m/s^2.
@seyll00 We may be talking about different questions. I was talking about the ones at the end where they talked about a ball that was being thrown. One of the questions asked about its velocity and acceleration at its maximum height, for example, and the correct answer would be zero and 9.8m/s^2 downwards. The questions I’m referring to didn’t have any diagrams; which one were you talking about?
Also, note that I did indicate direction in my post above (downwards); so if you’re referring to up as positive, then yes, 9.8m/s^2 downwards is equal to -9.8m/s^2.
EDIT: I don’t even remember seeing a diagram. I’m referring to the set of questions near the end where they were like "what could be possible velocity/displacement/acceleration (1) when the ball is thrown, (2) when it is at its maximum, and (3) right before it hits the ground, if I’m remembering correctly. Also, I’m pretty sure they didn’t have a negative and positive value, but simply used the terms “upwards” and “downwards.” Could be remembering wrong though.
@“Muhammad Sheheryar Naveed” Height was 1000m. Plane’s velocity was 50m/s. Since both PE = mgh and KE = .5mv^2 have ‘m’ in them, we can cancel the mass and just find the ratio of PE to KE.
PE = gh = 10 x 1,000 = 10,000 J
KE = .5v^2 = .5(50^2) = 1,250 J
The ratio of PE to KE is close to 10:1, so it is safe to say that the plane had more PE than KE.
@seyll00 I said negative as well because of the axis
@gmanhax it did have an axis if we are talking about the same questions. like the velocity when it is thrown downwards in the first question was -17.9 m/s (because the only other answer was 0), and gravity was -9.8m/s^2
it couldnt be 0, so it had to be -17.9m/s, and gravity was negative and there was only one answer that satisfied both
Can someone remind me what the relativity question was again?
@thetennisking Weird. I don’t recall a question with a diagram like that at all. Was that near the end of the test for you (like 70-72)?
What did you guys get on the current carrying wire question? It was like the left wire had a current of I, the right a current of 2I and something about point P
I put that the right wire had to be two times farther than the left one from point P.
@bobthebuilder13 I got twice as far as well.
ok nice i got the same. does anyone remember the what optical instrument for the camera question?
The right answer was convex lens, but I just left that one blank. The other one with the diagram was diverging lens right?
thats what I said @bobthebuilder13
Wouldn’t it be plane mirror, since the incident rays were not parallel to the horizontal. If the plane mirror were turned sideways, the angles are reflected exactly how they entered.
Oh idk… I just searched it up on google. I thought it had to be a lens because only lenses produce real images. A concave mirror would also produce a real image, but it would be on the same side as object.
The first one was definitely converging lens, the camera one. however in the second one, I believed it was plane mirror since the angle of incident equaled the angle of reflection on both the top and the bottom
Light rays wouldn’t pass through a mirror to that extent. It has to be a lens in question, and a diverging one at that.
@skstanford It was diverging. Plane mirrors wouldnt let rays pass through
If it was a mirror, light rays wouldn’t be on the opposite side as the object, as @skstanford said. For the light rays to be on the other side of the object, it had to be a lens.
The thing was, the initial rays weren’t parallel to the floor, they were at an angle, and diverging lenses diverge if the initial rays are parallel. The ones that are at an angle pass right through the lens.
If the plane mirror was rotated 90 degrees, it would not let light rays pass through and would work.