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daser333 [38]
3 years ago
8

A car of mass 900 Kg is moving with a velocity of 10 m/s. It is brought to rest at 25 m distance by applying the brakes. Calcula

te the acceleration. Why is it negative? How much force is required to stop the car?​
Physics
1 answer:
Verizon [17]3 years ago
3 0

Answer:

Assumption: the acceleration of this vehicle is constant until it comes to a stop.

Acceleration: (-2)\; \rm m\cdot s^{-2}.

The acceleration of this vehicle is negative because the velocity of this vehicle is decreasing over time.

Explanation:

  • Let u denote the initial velocity of this vehicle. u = 10\; \rm m\cdot s^{-1}.
  • Let v denote the final velocity of this vehicle. v = 0\; \rm m\cdot s^{-1} as the vehicle has come to a stop.
  • Let x denote the displacement of this vehicle. x = 25\; \rm m.
  • Let a denote the acceleration of this vehicle. The value of a\! needs to be found.

Assume that the acceleration of this vehicle, a, is constant. The SUVAT equations would apply.

The time t required for braking is neither given nor required. Hence, make use of the SUVAT equation v^{2} - u^{2} = 2\, a\, x to relate u, v, a, and x\!.

Rearrange this equation to find an expression for a, the acceleration of this vehicle:

\begin{aligned}a &= \frac{v^{2} - u^{2}}{2\, x} \\ &= \frac{(0\; \rm m\cdot s^{-1})^{2} - (10\; \rm m \cdot s^{-1})^{2}}{2\times (25\; \rm m)} \\ &= \frac{0^{2} - 10^{2}}{2 \times 25}\; \rm m \cdot s^{-2} \\ &= -2\; \rm m\cdot s^{-2}\end{aligned}.

  • When the rate of change of a value is greater than 0, that value would become larger over time.
  • When the rate of change of a value is equal to 0, that value would be constant.
  • When the rate of change of a value is smaller than 0, that value would become smaller over time.

Acceleration is the rate at which velocity changes over time.

The velocity of the vehicle in this question is getting smaller over time. Hence, the rate of change of the velocity of this vehicle (that is, the acceleration of this vehicle) would be a negative number.

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AveGali [126]

As the distance between two charged objects increases, the strength of the electrical force between the objects  <em>decreases</em>.

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3 years ago
A bowling ball of mass 5 kg rolls down a slick ramp 20 meters long at a 30 degree angle to the horizontal. What is the work done
Elena-2011 [213]

Answer:

The work done by gravity during the roll is 490.6 J

Explanation:

The work (W) is:

W = F*d

<em>Where</em>:

F: is the force

d: is the displacement = 20 m

The force is equal to the weight (W) in the x component:

F = W_{x} = mgsin(\theta)

<em>Where:</em>

m: is the mass of the bowling ball = 5 kg

g: is the gravity = 9.81 m/s²    

θ: is the degree angle to the horizontal = 30°        

F = mgsin(\theta) = 5 kg*9.81 m/s^{2}*sin(30) = 24.53 N    

Now, we can find the work:

W = F*d = 24.53 N*20 m = 490.6 J      

Therefore, the work done by gravity during the roll is 490.6 J.

I hope it helps you!

6 0
3 years ago
A girl weighing 50 kgf wears sandals of pencil heel of area of cross section 1 cm^2, stands on the floor.An elephant weighing 20
Klio2033 [76]

Answer:

\boxed{{\boxed{\blue{ 12.5}}}}

Explanation:

Given, for girl : Weight or force;

\rm \: F_1 = 50 \: kgf

Area of both heels;

\rm \: A_1 =  \; 2 ×1 \;  cm^2 = 2  \: cm^2

\rm \: Pressure \:  P_1  =  \cfrac{F_1}{ A_1 }  =  \dfrac{50 \: kgf}{2 \: cm {}^{2} }  = 25 \: kgf \: cm {}^{ - 1}

For elephant, Weight = Force \rm F_2 = 2000 kg•f

Area of 4 feet;

\rm \: A_2  = \; 4 \times 250 \;  cm^2 = 1000 \:  cm^2

\rm \: Pressure \:  P_2 = {F_2}/{A_2} \;  = \cfrac{2 \cancel{0 00 }\:  kgf}{1 \cancel{000} \: cm^2} =  2 \: kgf \: { \:cm}^{- 1}

Now;

\rm  = \dfrac{Pressure \:  Exerted  \: by  \: the \:  Girl}{Pressure  \: exerted  \: by \:  the  \: elephant}

=  \rm \: P_1/P_2

\implies    \rm\cfrac{25 \: kgf \: \: cm {}^{ - 2} }{2 \: kgf \: cm {}^{ - 2} } =  \rm\cfrac{25 \:  \cancel{kgf \: \: cm {}^{ - 2}} }{2 \: \cancel{ kgf \: cm {}^{ - 2}} } = \boxed{12.5}

Thus, the girl's pointed heel sandals exert 12.5 times more pressure P than the pressure P exerted by the elephant.

I aspire this helps!

3 0
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Answer:

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Explanation:

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   3        -43.2

The sign indicates that the positive sense is up

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