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# Tag Archives: t2

## Velocity and acceleration of a Ferrari !

A Ferrari covers120m from a standing start in 6sec at constant acceleration.Find its final velocity

u=0 (Since it starts from rest)

t= 6s

s=120m

a=?

v=?

from $\LARGE S=ut+\frac{1}{2}at^{2}$

$\LARGE a=\frac{2S}{t^{2}}$

a=2 x 120/36=6.67 m/s2

from v=u+at

v=40m/s

## Motion under gravity and time of fall

A body of mass m1 and another body of mass m2 are dropped from wqual heights.If time taken by the balls are t1 and t2 respectively then t1=t2. How ?

The acceleration due to gravity is independent of mass of body. When two different masses  are dropped from the  same height, they will take same time  to reach the surface of earth.

## A body is dropped from a tower of height 96 m. Another body is thrown up from the ground after a second with a velocity of 40 m/s.When and where they will meet?

A body is dropped from a tower of height 96 m. Another body is thrown up from the ground after a second with a velocity of 40 m/s. When and where they will meet?

For the first body,

u=0 m/s

Let S=x (from top)

x=0.5 gt ————— (1)

For the second body,

u=40 m/s

a=-g

S=96-x

96-x=40 t -0.5 gt2 ———–(2)

(1) + (2) =>

96=40t

or

t=96/40 = 2.4 s

x= 0.5 g t=28.224 m from top (taking g = 9.8 m/s2)

## Problem from relative velocity

A Boat covers certain distance between two spots in a river taking t1 hrs going downstream and t2 hrs going upstream. What time will be taken by boat to cover same distance in still water?

posted by STUTI

$t=\frac{2t_{1}t_{2}}{t_{1}+t_{2}}$