1. What is the average speed of a cheetah that sprints 100 m in 4 seconds? How about if it sprints 50 m in 2 s?

Question

2. If a car travels with an average speed of 60 km/h for an hour, it will cover a distance of 60 km.

a. How far would it travel if it moved at this rate for 4 h?

b. For 10 h?

3. In addition to the speedometer on the dashboard of every car, there is an odometer, which records the distance traveled. If the initial reading is set at zero at the beginning of a trip and the reading is 40 km one-half hour later, what was the car’s average speed?

4. Would it be possible to attain this average speed and never go faster than 80 km/h?

Accepted Answer

(Are you reading this before you have formed a reasoned answer in your mind? Think before you read answers. You’ll not only learn more; you’ll enjoy learning more.)

1. In both cases the answer is 25 m/s:

[latex]\begin{aligned}& ext { Average speed }=\frac{ ext { total distance covered }}{ ext { travel time }} \&\qquad=\frac{100 ext { meters }}{4 ext { seconds }}=\frac{50 ext { meters }}{2 ext { seconds }}=25 m / s\end{aligned}[/latex].

2. The distance traveled is the average speed [latex] imes[/latex] time of travel, so

a. [latex] ext { Distance }=60 km / h imes 4 h =240 km[/latex]

b. [latex] ext { Distance }=60 km / h imes 10 h =600 km[/latex]

3. [latex] ext { Average speed }=\frac{ ext { total distance covered }}{ ext { travel time }}=\frac{40 Km}{0.5 h}=80Km/h[/latex]

4. No, not if the trip starts from rest and ends at rest. During the trip, there are times when the instantaneous speeds are less than 80 km/h, so the driver must at some time drive faster than 80 km/h in order to average 80 km/h. In practice, average speeds are usually much lower than high instantaneous speeds.

Question 4.S&C.8: 1. What is the average speed of a cheetah that sprints 100 m...

Related Answered Questions