Help me read a position versus time graph and finding relations with acceleration and speed?

Question

A car travels a certain distance along a straight road (in the +x direction). The distance the car travels as a function of time is shown in the figure below.

When the car changes speed it does so uniformly.

Select the appropriate choice for each statement: T-True, F-False, G-Greater than, L-Less than, E-Equal to. (If the first is T, the second is G, and the rest E, enter TGEEEE). ( .... means blank)

Here is the graph:

http://capa.hep.uprm.edu/msuphysicslib/Graphics/Gtype05/prob16a_accelx2.gif

A) The speed is ..... zero at 23 sec.

B) The x-acceleration is ..... zero at 38 sec .

C) At 52 sec, the speed is as high as it gets.

D) The acceleration magnitude at 38 sec is ..... the acceleration magnitude at 15 sec.

E) The x-acceleration is ..... zero at 10 sec .

F) The speed at 52 sec is ..... the speed at 76 sec.

I'd appreciate some help. These relations are confusing me.

I have already tried:

EGTEGL

GGFGGL

EGTGGG

EGTGGL

EGTEGG

EGFGGG

EGFEGG

Answer 1

EGTGEG (your 3rd answer is closest to the correct answer).

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A) The speed is ..E... zero at 23 sec. {The car is not advancing in distance with time, so the speed is zero}

B) The x-acceleration is ...G.. zero at 38 sec .{ The car is picking up speed from zero speed to something higher. "Picking up speed" is the same as accelerating}.

C) At 52 sec, the speed is as high as it gets...TRUE. {This is the steepest part of the curve which means you go the furthest distance for a given amount of time}

.

D) The acceleration magnitude at 38 sec is ..G... the acceleration magnitude at 15 sec.{ At fifteen seconds the car is slowing down which implies a negative acceleration. At 38 seconds the car is speeding up which implies a positive acceleration. Positive numbers are bigger than negative numbers}

E) The x-acceleration is ..E... zero at 10 sec .{ The speed at ten seconds is constant since the curve is a straight line. So if speed is constant, then acceleration is zero because you are not speeding up or slowing down. NOTE acceleration is equal to zero, speed is NOT equal to zero}.

F) The speed at 52 sec is ...G.. the speed at 76 sec. {The curve is rising at a much faster rate at 52 seconds compared to 76 seconds}

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I'm fairly certain that I've given you the correct answer. However, if that doesn't work, try EGTEEG (which you haven't tried yet). E-mail if you are still having problems.

Answer 2

The best I can tell the answers are TGTETG.