Question

Question 2 A bus decreases its speed from 80 km h −1 to 60 km h −1 in 5 s. Find the acceleration of the bus.

Class 9 - Science - Motion Page 103

Answer 1

Acceleration of the bus is :a=−109 ms

Explanation:

acceleration of an object is described as :a=ΔvΔt

Δv=60−80=−20kmh

Δt=5s

Here we are converting the units to ms:

−20 kmh=−20.0003600=−20036=−509ms

a=ΔvΔt

a=−5095

a=−509⋅15

a=−109 ms2

Answer 2

Hello!
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Initial speed (u) = 80 km/hr
km/hr to m/s = × $\frac{5}{18}$
Therefore,
80 × $\frac{5}{18}$ = 22.22m/s

Final speed (v) = 60km/hr
km/hr to m/s = × $\frac{5}{18}$
Therefore,
60 × $\frac{5}{18}$ = 16.66m/s

Time (t) = 5s

Acceleration (a) = $\frac{v-u}{t}$
                          = $\frac{16.66-22.22}{5}$
                          = 1.112m/s$^{2}$
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HOPE THIS HELPS YOU :)