Question

PLS.ANSWER MY QUESTIONS 1 TO 4 AS FAST AS POSSIBLE......

Answer 1

answers in attachment

Answer 2

Hey Mate !

Here is your solution :

1.

Initial velocity ( u ) = 0

Final velocity ( v ) = 40 km/h

Time ( t ) = 10 s = ( 1/360 ) h

As , 60 min = 1 h

And,

1 min = 60 sec,

So,

=> 60 × 60 sec = 1 h

=> 1 sec = ( 1 / 60 × 60 ) h

=> 1 sec = ( 1 / 3600 ) h

=> 10 sec = ( 10 / 3600 ) h = ( 1/360 ) h

Now,

=> Acceleration ( a ) = ( v - u ) / t

= ( 40 km/h - 0 ) / ( 1 / 360 )h

= ( 40 km/h ) × ( 360 ) × ( 1/h )

= 14,400 km / h^2

= 14,400 km h^( -2 )

2nd Part :

Initial velocity ( u ) = 0

Final velocity ( v ) = 40 km/h

Time ( t ) = 10 sec.

To convert ( 40 km/h ) in ( m/s )

We know that,

=> 1 km = 1,000 m -------- ( 1 )

And,

=> 1 h = 3,600 sec ----------- ( 2 )

By dividing ( 1 ) by ( 2 ),

=> ( 1 km ) / ( 1 h ) = ( 1,000 m ) / ( 3,600 s )

=> 1 km/h = ( 5/18 ) m/s

As, 1 km/h = ( 5/18 ) m/s

So, 40 km/h = ( 5 × 40 / 18 ) m/s

= ( 100/9 ) m/s

=> Acceleration ( a ) = ( v - u ) / t

= { ( 100/9 ) m/s - 0 } / 10 s

= ( 100/9 ) × ( 1/10 ) × ( m/s ) × (1/s )

= ( 10/9 ) m/s^2

= 1.11 m/s^2 or 1.11 ms^( -2 ).

2.

Given,

Initial velocity ( u ) = 60 km/h

Final velocity ( v ) = 0

Time = 20 s

Now,

As , 1 km/h = ( 5/18 ) m/s

So, 60 km/h = ( 5 × 60 / 18 ) m/s

= ( 50/3 )m/s

=> Acceleration ( a ) = ( v - u ) / t

= { 0 - ( 50/3 )m/s } / 20 s

= ( -50 / 3 ) × ( 1 /20 ) m/s^2

= ( -2.5 / 3 ) m/s^2

= - 0.83 m/s^2 or -0.83 ms^( -2 )

3.

Well , Retardation is negative Acceleration.

Given,

Initial velocity ( u ) = ?

Final velocity ( v ) = 0

Time ( t ) = 10 s

Acceleration ( a ) = -2 m/s^2

Using 1st equation of Motion ,

=> v = u + at

=> u = v - at

=> u = 0 - ( -2 m/s^2 ) × 10 s

=> u = ( 2 m/s^2 ) × 10 s

=> u = ( 2 × 10 × m × s ) /s^2

=> u = 20 m/s or 20 ms^( -1 ).

4.

Given,

Initial velocity ( u ) = 54 km/h = 15 m/s

Final velocity ( v ) = 72 km/h = 20 m/s

Time = 15 s

Acceleration = ?

As , 1 km/h = ( 5/18 ) m/s

So, 54 km/h = ( 5 × 54 / 18 ) m/s

= 15 m/s

So, 72 km/h = ( 5 × 72 / 18 ) m/s

= 20 m/s

=> Acceleration ( a ) = ( v - u ) / t

= { ( 20 m/s ) - ( 15 m/s ) } / 15 s

= ( 5 m/s ) × ( s / 15 )

= ( 1/3 ) m/s^2

= 0.33 m/s^2 or 0.33 ms^( -2 )

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Hope it helps !! ^_^