a car is 4m long ,crosses a 20m bridge in 1.6seconds .at what speed was the car running.
Answers
Answer:
Step-by-step explanation:
I'll start with the distance covered while decelerating. Since you know that the initial speed of the car is 15.0 m/s, and that its final speed must by 10.0 m/s, you can use the known acceleration to determine the distance covered by
v
2
f
=
v
2
i
−
2
⋅
a
⋅
d
Isolate
d
on one side of the equation and solve by plugging your values
d
=
v
2
i
−
v
2
f
2
a
d
=
(
15.0
2
−
10.0
2
)
m
2
s
−
2
2
⋅
2.0
m
s
−
2
d
=
31.3 m
To get the time needed to reach this speed, i.e. 10.0 m/s, you can use the following equation
v
f
=
v
i
−
a
⋅
t
, which will get you
t
=
v
i
−
v
f
a
t
=
(
15.0
−
10.0
)
m
s
2.0
m
s
2
=
2.5 s
SIDE NOTE I left the value I got for the distance rounded to three sig figs.I'll start with the distance covered while decelerating. Since you know that the initial speed of the car is 15.0 m/s, and that its final speed must by 10.0 m/s, you can use the known acceleration to determine the distance covered by
v
2
f
=
v
2
i
−
2
⋅
a
⋅
d
Isolate
d
on one side of the equation and solve by plugging your values
d
=
v
2
i
−
v
2
f
2
a
d
=
(
15.0
2
−
10.0
2
)
m
2
s
−
2
2
⋅
2.0
m
s
−
2
d
=
31.3 m
To get the time needed to reach this speed, i.e. 10.0 m/s, you can use the following equation
v
f
=
v
i
−
a
⋅
t
, which will get you
t
=
v
i
−
v
f
a
t
=
(
15.0
−
10.0
)
m
s
2.0
m
s
2
=
2.5 s
SIDE NOTE I left the value I got for the distance rounded to three sig figs.