Question

name_________________________period_____
calculating speed

problems

1. a runner completes a 6000m race in 841s. what is her speed?

1. if you travel in a car at 85km/hr. for 0.5 hours, how far have you gone?

1. in canada, the speed limit is 100km/hr on highways. if a car goes 220km in 1.5 hours, was this car speeding?

Explanation:

Step1: Recall speed formula

Speed $s = \frac{\text{distance }d}{\text{time }t}$

Step2: Solve problem 1

Substitute $d=6000\text{ m}$, $t=841\text{ s}$:
$s = \frac{6000}{841} \approx 7.13\text{ m/s}$

Step3: Recall distance formula

Distance $d = s \times t$

Step4: Solve problem 2

Substitute $s=85\text{ km/hr}$, $t=0.5\text{ hr}$:
$d = 85 \times 0.5 = 42.5\text{ km}$

Step5: Calculate car's speed (problem3)

Substitute $d=220\text{ km}$, $t=1.5\text{ hr}$:
$s = \frac{220}{1.5} \approx 146.67\text{ km/hr}$

Step6: Compare to speed limit

$146.67\text{ km/hr} > 100\text{ km/hr}$, so the car was speeding.

Answer:

1. Approximately 7.13 m/s
2. 42.5 km
3. Yes, the car was speeding.