Multiple choice velocity/acceleration

[williamx11373]

a strobe photograph of a car moving along a straight road shows the interval between each successive image to be diminishing. If the direction of motion of the car is taken as positive, which of the following are negative?

a. the speed of the car
b. the average velocity of the car
c. the average acceleration of the car
d. all of the above


i never learned what a strobe photograph is, but I am guessing it is C. because it is slowing down and therefore diminishing.

is that correct ?

 

[CompuChip]

A strobe photograph is basically an image in which multiple photos are overlayed, taken at fixed time intervals. I bet you have seen them before, like this one.

So in the question what they basically say is that the distance covered in the same time interval (say, 1 second) decreases.

Using what you know about physics (e.g. the s = v t and 1/2 a t^2 formulas for different types of motion) can you try to reason what is going on with the velocity and acceleration, and try to back your statement?

 

[kerimek]

Yes, that is correct. The average acceleration of the car would be negative because the car is slowing down, meaning its velocity is decreasing over time.