# physics

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What average force in N is required to stop an 1,188 kg car in 9 s if it is initially traveling at 89 km/h?

f=ma
f=1,188(9.8)
f=11642.4N

This looks wrong to me. Can someone explain this to me.

• physics -

Why did you choose 9.8 as the acceleration? It is not falling.

its average velocity during stopping is 89/2 km/hr (change that to m/s)

So it traveled in that time a distance of avgvelocity*9s...

force*distance=initial KE= 1/2 m vi^2
change vi to m/s, then solve for force.

• physics -

Firstly F=ma but a=(v-u)/t. First convert the 89 Km/h into m/s.

89x1000/3600=24.72m/s

Then using F=m(v-u)/t
F=1188(24.72-0)/9
F=3263.04N

• Physics -

What is the average force need to stop a 1500 N car in 8.0 S if it is traveling at 90 km/hr?

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