Question

A body covers a distance of 4 m is 3^rd second and 12 m in 5^th second. If the motion is uniformly accelerated, how far will it travel in the next 3 second?

• A. 10m
• B. 30m
• C. 40 m
• D. 60m

Answer 1

Answer: (D)

60m

Answer 2

$S _ { 3 } = u + \frac { a } { 2 } ( 2 \times 3 - 1 ) = 4$

Or $u + \frac { \pi } { 2 } a = 4$

$\mathrm { S } _ { 5 } = \mathrm { u } + \frac { \mathrm { a } } { 2 } ( 2 \times 5 - 1 ) = 12$

Or $u + \frac { 9 } { 2 } \mathrm { a } = 12$

On solving , u = $- 6 \mathrm {~ms} ^ { - 1 } , \mathrm { a } = 4 \mathrm {~ms} ^ { - 2 }$

Distance travelled in next 3 seconds $= \mathrm { S } _ { 8 } - \mathrm { S } _ { 5 }$

$= \left[ - 6 \times 8 + \frac { 1 } { 2 } \times 4 \times ( 8 ) ^ { 2 } \right] - \left[ - 6 \times 5 + \frac { 1 } { 2 } \times 4 \times ( 5 ) ^ { 2 } \right]$

= 80 - 20 = 60 cm