    AP Physics B

Ever see an object roll UP hill? C. Solving Word Problems ex) A car produces a 92 m skid mark with a deceleration of 7.00 m/s2. What speed was the car travelling just before it applied the brakes?

Vi = ?

a = -7.00 m/s2

Vf = 0

Δd = 92 m Vf2 = Vi2 + 2aΔd

0 = Vi2 + 2(-7.00 m/s2)92 m

Vi2 = 1288

Δd = 36 m/s `	`
` `

ex) A car accelerates uniformly from rest at a rate of +10 m/s2. How far will the car travel in 4 seconds?

Step 2 - Turn all your information into letters

Vi = 0 (starts from rest)

a = +10 m/s2

t = 4 seconds

d = ?

Step 3 - Substitute and Solve Equation: Δd = Vit + 1/2aΔt2

= 0 m/s(4 sec)+1/2(10 m/s2)(4s)2

Δd = 0 + 5(16)

Δd = 80 m ` `
` ` Ex) If a car traveling 20 mph can stop in about 40 ft. If the same car was traveling twice as fast, how far would it take to stop?

Vf2 = Vi2 + 2aΔd

0= Vi2 + 2aΔd

-Vi2  = 2aΔd

4 times further

160 ft  Displacement,  Plots  ©Tony Mangiacapre., - All Rights Reserved [Home]
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