A driver of a car travelling at 54 km per hour apply the brakes and accelerates uniformly in the opposite direction the car stop in 5 second another driver of another car travelling at 36 km per hour apply is break slowly and stop in 10 on the the same graph paper plot the speed versus time graphs for the two car before stopping.
Pls answer as fast as u can!
Answers
Distance covered by car₁ = 37.5 m and distance covered by car₂ = 50 m
Solution
For car 1 :
Initial speed of car = 54 km/h
= 54 × (5/18) m/s
= 15 m/s
As it comes to stop, final speed of car i.e. v = 0 m/s
Timd taken to stop = 5 seconds.
We will use 1st equation of motion :
◕ v = u + at
⇒ 0 = 15 + a × 5
⇒ 5a = -15
⇒ a = -15/5
⇒ a = -3 m/s²
[Note : Negative sign shows retardation ]
Now we will use 2nd equation of motion :
◕ s = ut + ½ at²
⇒ s = 15 × 5 + ½(-3) × 5²
⇒ s = 75 + ½(-3) × 25
⇒ s = 75 + ½(-75)
⇒ s = 75 - 37.5
⇒ s = 37.5 m
∴ Distance covered by car₁ = 37.5 m
Now for car 2 :
Initial speed of car = 36 km/h
= 36 × (5/18) m/s
= 10 m/s
Final speed of car = 0 m/s [As it comes to stop]
Time taken to stop = 10 seconds.
We will use 1st equation of motion to find acceleration :
◕ v = u + at
⇒ 0 = 10 + a × 10
⇒ 10a = -10
⇒ a = -10/10
⇒ a = -1 m/s²
[Negative sign shows retardation, working against the motion ]
Now we will use 3rd equation of motion to find distance covered by car₂ :
◕ v² - u² = 2as
⇒ 0² - 10² = 2s × (-1)
⇒ -100 = -2s
⇒ s = -100/-2
⇒ s = 50 m
∴ Distance covered by car₂ = 50 m