Phy (F.4 )

The above equations are right ,but he still had not changed the answer for question(1)and (2) to kmh-1

(a) Find the maximum speed of the car . Express the answer in kmh-1.
First we have the following equation:
v=u+at
V is the maximum speed of the car, u is the initial speed of the car, a is the acceleration, and t is the time
as the starting speed is 0, so u=0
v=u+at
v=0+(6)(4)
v=24ms-1
v=24/1000*60*60
= 86.4km -1
so the maximum speed is 86.4km -1
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(b)Find the final speed of the car.Express the answer in kmh-1
after reaching the maximum speed of v=24ms-1,it started to decelerate:
v=u+at
v=24+(-4)(2)
v=16ms-1
=16/1000*60*60
=57.6kmh-1
so the final speed is 57.6kmh -1
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c)Find the average acceleration of the car. Express the answer in ms-2
a=Δv/Δt
a=(final speed-initial speed)/(time taken over the movement)
a=(16 -0)ms-1/(4+2)s
a=2.67ms-2
so the average acceleration of the car is 2.67ms-2

(a) v=u+at
v=0+6*4
v=24ms-1
v=24*3600/1000 kmh-1
v=86.4kmh-1

(b) v=u+at
v=24+(-4)(2)
v=16ms-1
v=16*3600/1000 kmh-1
v=57.6kmh-1

(c)v=u+at
16=0+6a
a=2.67ms-2 (to 3 sig. fig.)