What are some sample constant velocity problems?

1 Answer
Dec 27, 2014

When you have constant velocity, it usually makes your physics problems a lot easier. This is because you don't need to take into account acceleration, and that simplifies a lot of things.

When you ask for sample problems, I assume that you want kinematics problems. So here's a couple I just thought of out of the top of my head. I'll solve them out here as well. So you could just try the problem by yourself, and then look at the solution to see if it's right.

The main equation you will use for these is

#Deltax = v_ot#

Where #Deltax# is the displacement, #v_ot# is initial (and constant) velocity, and #t# is time.

  • If a car moves at a constant rate of 5 meters per second, what distance does it reach in 45 seconds?

Just plug everything into the equation:

#Deltax = 5(45) = # 225 meters

  • If a man walks a distance of 1 kilometer in 10 minutes at constant velocity, what is his velocity?

Before you do this, make sure that you've converted everything to the right units. 1 kilometer = 1000 meters, and 10 minutes = #10*60/1 = 600# seconds

Now we just plug in and solve:

1000 = #v_o#*600

#v_o = 1000/600 = #1.667 meters per second

  • Can an object have nonzero speed but zero velocity?

To know the answer to this, you need to know your definitions inside out. Speed is a scalar, and represents distance covered over time. Velocity, on the other hand, is a vector, and represents displacement over time.

Now you just have to think through it logically: is there any situation in which an object covers some distance but does not have any displacement?

And then the answer becomes clear: when an object is moving the same distance backwards and forwards, or moving around in circles, then it does indeed have a speed, but it's velocity is zero as it's displacement is zero.

  • A truck is moving at a constant velocity of 80 meters per second. It needs to rush to a town that is 25 kilometers away in 5 minutes to ensure that their delivery is on time. Will they make it?

Again, first we convert our units:

25 km = 25000 m
5 minutes = 300 seconds

Now we plug in and evaluate. This time it will be a little different though. Because we know that they need to make it in a maximum of 5 minutes, we can say that #v_ot# has to be greater than or equal to #Deltax#.

#25000 ≤ 80(300)#

#25000 ≤ 24000# X

Since the equation is not satisfied, we know that the truck will not make it in time.

If you want more problems, I recommend this website called http://www.physicsclassroom.com/.

Hope that helps :)