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solong [7]
3 years ago
13

A car is running at the speed of 45km/hr see a child 25 meter ahead and suddenly apllies a brakes. If the retradation of the car

is 2 meter per second square,is the child spared?
Physics
1 answer:
kenny6666 [7]3 years ago
4 0

Answer:

The car stops in 7.78s and does not spare the child.

Explanation:

In order to know if the car stops before the distance to the child, you take into account the following equation:

x=x_o+v_ot-\frac{1}{2}at^2        (1)

vo: initial speed of the car = 45km/h

a: deceleration of the car = 2 m/s^2

t: time

xo: initial distance to the child = 25m

x: final distance to the child = 0m

It is necessary that the solution of the equation (1) for time t are real.

You first convert the initial speed to m/s, then replace the values of the parameters and solve the quadratic polynomial for t:

45\frac{km}{h}*\frac{1h}{3600s}*\frac{1000m}{1km}=12.5\frac{m}{s}

0=25+12.5t-2t^2\\\\2t^2-12.5t-25=0\\\\t_{1,2}=\frac{-(-12.5)\pm \sqrt{(-12.5)^2-4(2)(-25)}}{2(2)}\\\\t_{1,2}=\frac{12.25\pm 18.87}{4}\\\\t_1=7.78s\\\\t_2=-1.65s

You take the first value t1 because it has physical meaning.

The solution for t is real, then, the car stops in 7.78s and does not spare the child.

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How much displacement will a spring with a constant of 120N / m achieve if it is stretched by a force of 60N?
Andrew [12]

Answer:

Explanation:

There's a formula for this:

F = k*displacement

F being force, k being the spring constant, and displacement being the change in x

We are given the force and the spring constant, so this is essentially isolating the Δx term. Do 60N/120N per meter. The newtons cancel out and you get a final answer of Δx = 0.5 meters

3 0
3 years ago
A mother and her 35.0 -kg child are riding an escalator to the third level of a shopping mall. If the child's gravitational pote
notka56 [123]

The increase in potential energy of his mother if her mass is 56.0 kg will be 6031.97 J.

<h3>What is gravitational potential energy?</h3>

The energy that an item has due to its location in a gravitational field is known as gravitational potential energy.

The potential energy increases by 3773 J

PE₂-PE₁=mg(h₂-h₁)

3773 J = 35.0 × 9.81 × (h₂-h₁)

(h₂-h₁) = 10.98

Case 2 ;

ΔPE =?

ΔPE=mg(h₂-h₁)

ΔPE=56.0 × 9.81 ×10.98

ΔPE=6031.97 J.

Hence, the increase in potential energy of his mother if her mass is 56.0 kg will be 6031.97 J.

To learn more about the gravitational potential energy, refer;

brainly.com/question/3884855#SPJ1

#SPJ1

8 0
1 year ago
If eight water waves pass an ocean buoy each minute, and successive wave crests are 20 m apart, find the wave speed:____________
Llana [10]

Answer:

The wave speed is calculated below:

Explanation:

Given,

number of waves passed per minute = 8

time period = 1 minute = 60 s

distance between successive wave crests = 20 m

waves passing interval per second = \frac{8}{60} s^{-1}

Now,

wave speed = 20 m × \frac{8}{60} s^{-1}

                     = \frac{8}3} m/s

                     = 2.67 m/s

Hence the wave speed is 2.67 m/s.

4 0
3 years ago
When working with a powered instrument, the swirling effect produced by the water stream within the confined space of a periodon
Lina20 [59]

Answer:

Acoustic microstreaming

Explanation:

Acoustic microstreaming is the swirling effect produced by water stream confined in a spaced of a periodontal pocket.

  • It is the movement of water in a particular direction as a result of mechanical pressure within the fluid body.
  • They are often used in dental procedures to remove particulates from the teeth.
  • It mostly relies on the properties of sound waves to achieve this goal
3 0
2 years ago
The barometer of a mountain hiker reads 930 mbars at the beginning of a hiking trip and 780 mbars at the end. Neglecting the eff
lara31 [8.8K]
We could use the change of pressure to calculate for the height climbed by the mountain hiker. The change of pressure is given by

p = rho * g * h, where p is the change of pressure, rho is the air density, g is the acceleration due to gravity, and h is the height.

Using the conversion 1 mbar = 100 Pa,

(930 - 780)(100) = (1.20)(9.80)h
15000 = 1.20*9.80*h

h = 1.28 km
6 0
3 years ago
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