Question

please answer..........​

Answer 1

Answer:

Force = 20833.34 N (approx)

Power = 12500 J/s or 12500 Watts

Explanation:

First we will convert the speed in m/s

90 km/h = 90 × 5/18 m/s

⇒ 90 km/h = 25 m/s

Now given that the car stops at a distance of 15 m from the point when one applies breaks.

So, s = 15 m

u = 25 m/s (given)

v = 0 m/s (since, the car stops)

So, from third equation of motion, we know

2as = v² - u²

⇒2a × 15 = 0 - 25²

⇒ 30a = - 625

⇒ a = - 125/6 m/s²

Negative sign indicates that there is a retardation.

Now, we know that F = ma

Mass = 1000 kg

⇒ Force = 1000 × (-125/6)

⇒ Force = - 20833.34 N (approx)

Negative sign means that the force is applied in opposite direction of motion.

Now, time = 25 s

Power = work/time

Work = force × displacement

Work = 20833.34 × 15

⇒ work =  312500 Joules (approx)

So, power = 312500/25

Power = 12500 J/s

Answer 2

Answer:

first we will convert the speed metre per second.

90km/h=90*5/18 m/s

=>90 km/h=25m/s

now given that the cost tops at the distance of 15 m from the point when one applies break.

so,

s=15m

u=25m/s

v=0m/s

show from third equation of motion we know that.

2as=v^2-u^2

2a*15=0-25^2

30a=-625

a=-125/6m/s^2

negative sign indicates that there is a retardation

now we know that f =ma

m=1000kg

F=1000*-125/6

F=-20833.34N(app)

negative sign means that the force is supplies in opposite direction of motion.

now

t=25s

p=w/t

w=F*D

w=20833.34*15

w=312500J

so,

p=312500/25

power=12500J/s