Respuesta :
Answer:
8.4m/s
Step-by-step explanation:
the information we are given is:
initial time: [tex]t_{1}=4s[/tex]
final time: [tex]t_{2}=8s[/tex]
thus, the interval of time is: [tex]t=t_{2}-t_{1}=8s-4s=4s[/tex]
according to the statement, the distance at a certain time is given by:
[tex]d(t)=0.7t^2[/tex]
To find the average distance we need to find first the total distance traveled in those 4 seconds .
At a time of 4 seconds ⇒ [tex]t_{1}=4s[/tex]
the distance at that time is:
[tex]d(4)=0.7(4)^2\\d(4)=0.7(16)\\d(4)=11.2m[/tex]
also, the distance at a time of 8 seconds ⇒ [tex]t_{2}=8s[/tex]
and the distance at this time is:
[tex]d(8)=0.7(8)^2\\d(8)=0.7(64)\\d(8)=44.8m\\[/tex]
Now we can find the distance traveled between 4 and 8 seconds:
[tex]d=d(8)-d(4)\\d=44.8m-11.2m\\d=33.6m[/tex]
and finally we use the formula for the average speed:
[tex]s=\frac{d}{t}[/tex]
where [tex]d[/tex] is the distance traveled in [tex]t[/tex] time:
[tex]s=\frac{33.6m}{4s} \\s=8.4m/s[/tex]
the average speed in meters per second: 8.4m/s
Answer:
8.4m/s
Step-by-step explanation:
Speed or velocity is defined as the change in distance of a body with respect to time. It is expressed as:
Speed = distance/time
Given distance d(t) = 0.7t²
When t = 4secs
d4) = 0.7 × 4²
d(4) = 11.2m
At t = 8secs
d(8) = 0.7× 8²
d(8) = 44.8m
Since speed = distance/time
Speed at t = 4secs = 11.2/4
= 2.8m/s
Speed at t = 8secs = 44.8/8
= 5.6m/s
average speed, in meters per seconds between 4 and 8 seconds after it was dropped will be ∆d/∆t
= 44.8-11.2/8-4
= 33.6/4
= 8.4m/s
