Question

solve this question no 7

with full explanation please​

Answer 1

We shall calculate the total distance by separating the different phases of the journey :

Part 1 :

Initial velocity = 0 m/s

Acceleration = 0.5 m/s²

Time = 20 secs

Hence distance be d1

$d1 = ut + \frac{1}{2} a {t}^{2}$

$= > d1 = 0 + \frac{1}{2} \times (0.5) \times {(20)}^{2}$

$= > d1 = 100 \: m$

Part 2 :

Car travels with constant velocity for 20 secs.

Velocity at end of 1st part be v

$v = u + at \: = 0 + (0.5) \times (20) = 10 \: m {s}^{ - 1}$

So distance travelled be d2 :

$d2 = v \times t = 10 \times 20 = 200 \: m$

Part 3 :

Car decelerates by brakes in 10 seconds.

So final velocity is zero.

Let acceleration be a

$a = \dfrac{0 - 10}{10} = - 1 \: m {s}^{ - 2}$

So distance be d3 :

$d3 = ut + \frac{1}{2} a {t}^{2}$

$= > d3 = (10 \times 10) + \frac{1}{2} ( - 1) \times {(10)}^{2}$

$= > d3 = 100 - 50 = 50 \: m$

So total distance :

$D = d1 + d2 + d3$

$= > D = 100 + 200 + 50$

$= > D = 350 \: m$

Answer 2

Explanation:

$\bf \huge \: \: Question \: \:$

a car initially at Rest to given a uniform acceleration of 0.5 m/S2 for 20 sec .then the car moves in uniform acceleration for 20 sec . the brakes are then applied and brought to rest in 10 sec and brought to rest . find the total distance covered

________________________

$\bf \huge \: \: Given \: \:$

• u=10 sec .
• t 1=20 sec .
• t 2=10 sec .
• a=0.5m/s^2

________________________

$\bf \huge \: \: To \: Find \:$

• the total distance covered

________________________

$\bf \:We \: Have\:$

$\bf \:S=ut+1/2at^2\:$

Then Putting the value:-

$\bf \:=10×20+1/2×0.5×10^2\:$

$\bf \:=200+100\:$

On Adding

$\bf \red{=300m}\:$

$\bf \:We \: Have\:$

$\bf \:V=u+at\:$

Then Putting the value:-

$\bf \:0=10+a×10\:$

$\bf \:a=-1m/s^2\:$

$\bf \:V^2=u^2+2as\:$

$\bf \:0=100+2×-1×s\:$

$\bf \red{S=50m}\:$

$\bf \</u></strong><strong><u>r</u></strong><strong><u>e</u></strong><strong><u>d</u></strong><strong><u>{</u></strong><strong><u>Total</u></strong><strong><u>. </u></strong><strong><u> </u></strong><strong><u>S</u></strong><strong><u>=</u></strong><strong><u> </u></strong><strong><u>5</u></strong><strong><u>0</u></strong><strong><u>m</u></strong><strong><u>+</u></strong><strong><u>3</u></strong><strong><u>0</u></strong><strong><u>0</u></strong><strong><u>m</u></strong><strong><u> </u></strong><strong><u>=</u></strong><strong><u> </u></strong><strong><u>3</u></strong><strong><u>5</u></strong><strong><u>0</u></strong><strong><u> </u></strong><strong><u>m</u></strong><strong><u>}</u></strong><strong><u>\:$

.