Concepts

Class 9
Chapter 8 Class 9 - Motion

it is denoted by

s = ut + Β½ at 2

Distance=Initial Velocity Γ Time + 1/2acceleration Γ time 2

Where

s = Distance Travelled

u = Initial Velocity

t = time taken

a = acceleration

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## Questions

Q 1 Page 109 - A bus starting from rest moves with a uniform acceleration of 0.1 m s-2 for 2 minutes. Find (a) the speed acquired, (b) the distance travelled

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Q 4 Page 110 - A racing car has a uniform acceleration of 4 m s-2. What distance will it cover in 10 s after start?

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NCERT Question 4 - A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 3.0 m sβ2 for 8.0 s. How far does the boat travel during this time?

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Example 8.6 - A car accelerates uniformly from 18 km hβ1 to 36 km h β 1 in 5 s.Calculate (i) the acceleration and (ii) the distance covered by the car in that time.

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Example 8.7 - The brakes applied to a car produce an acceleration of 6 m s-2 in the opposite direction to the motion. If the car takes 2 s to stop after the application of brakes, calculate the distance it travels during this time.

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### Transcript

Second Equation of Motion - Derivation s = ut + 1/2 ππ‘^2 Derivation πΓ We know that Velocity = π·ππ πππππππππ‘/ππππ Velocity Γ Time = Displacement Displacement = Velocity Γ Time If Velocity is not constant (i.e. Velocity keeps on increasing or decreasing) We can also take Average Velocity in place of Velocity So our formula becomes Displacement = Average Velocity Γ Time Displacement = (πΌπππ‘πππ π£ππππππ‘π¦ + πΉππππ π£ππππππ‘π¦)/2 Γ Time s = ((π’ + π£)/2) Γ t From first equation of motion, we know that: v = u + at Putting value of v in this equation s = ((π’ + (π + ππ))/2) Γ t s = ((2π’ + ππ‘)/2) Γ t s = (2π’/2+ππ‘/2) Γ t s = (π’+1/2 ππ‘) Γ t s = π’π‘+1/2 ππ‘^2