A driver of a car travelling at 52 km h–1 applies the brakes and accelerates uniformly in
the opposite direction. The car stops in 5 s. Another driver going at 3 km h–1 in another car
applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus
time graphs for the two cars. Which of the two cars travelled farther after the brakes were
applied?
solve this plz
Answers
Answer:
A
Explanation:
Initial speed of the car A u=52 kmh
−1
=52×
18
5
=14.44 ms
−1
The car stops in 5 seconds i.e v=0 at t=5
(A) : Initial speed of the car A u=3 kmh
−1
=3×
18
5
=0.83 ms
−1
The car stops in 10 seconds i.e v=0 at t=10
With the help of these initial and final points for both the cases, we can plot the graph of speed vs time.
Area under the speed-time graph gives the distance covered.
∴ Distance covered by car A x
A
=
2
1
×14.44×5=36.1 m
∴ Distance covered by car A x
B
=
2
1
×0.83×10=4.15 m
Thus car A travels more distance than B.
Answer:
Distance Travelled by first car before coming to rest =Area of Δ OPR
= (1/2) x OR x OP
= (1/2) x 5 s x 52 kmh-1
= (1/2) x 5 x (52 x 1000) / 3600) m
= (1/2) x 5x (130 / 9) m
= 325 / 9 m
= 36.11 m
Distance Travelled by second car before coming to rest =Area of Δ OSQ
= (1/2) x OQ x OS
= (1/2) x 10 s x 3 kmh-1
= (1/2) x 10 x (3 x 1000) / 3600) m
= (1/2) x 10 x (5/6) m
= 5 x (5/6) m
= 25/6 m
= 4.16 m