Speed and Velocity: Answers

Calculate the speed of a grasshopper when it jumps 2 meters in 0.5 seconds

To calculate speed, we need to divide the distance by the time.

Speed = distance / time.

2 / 0.5 = 4 m/s. Remember the units!

Look at the distance-time graph above. For how long was the red object travelling at a constant speed? Calculate its overall speed for the whole journey.

In a distance-time graph, the sloped lines indicate that an object is travelling at a constant speed. In the graph, we can see that the red object travels at a constant speed for about 10 seconds. It then remains stationary for a further ten seconds. To calculate the overall speed, we do distance divided by time. The red object has travelled a distance of 10 meters in 20 seconds, so its speed is 10/20 = 0.5 m/s.

Is velocity a scalar or a vector quantity and what does this mean?

A scalar quantity just has magnitude whereas a vector quantity has both magnitude and direction. Velocity means speed in a certain direction, so this is a vector quantity.

How would you calculate the total distance travelled from a velocity-time graph?

For a velocity-time graph, you can calculate the distance travelled by calculating the area underneath the graph. The easiest way to do this is to divide the space underneath the lines into separate triangles and rectangles, calculating the area of these shapes and adding these areas together. Remember that area of a rectangle is equal to base x height and the area of a triangle is (base x height)/2.