1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
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.

You might be interested in
A light wave travels through air at a speed of 3.0x108 m/s. Green light has a wavelength of about 5.76x1014Hz. What is the wavel
solong [7]

Answer:

521 nm

Explanation:

Given the values and units we are given, I'm assuming  5.76*10^14 Hz is frequency.

The formula to use here is λ * υ = c, where λ is wavelength, υ is frequency, and c is the speed of light.

λ = \frac{3*10^8\frac{m}{s} }{5.76*10^{14}Hz} = {5.20833*10^{-7} m}\approx{521 *10^{-9}m}={521 nm}

4 0
2 years ago
Sound waves travel at the rate of 343 m/s at 20°C. If a man standing 450 meters away from the wall of a canyon yells, “Hello,” h
nekit [7.7K]

Answer:

2.62seconds

Explanation:

Speed is defined as the ratio of the distance covered by a body with respect to time.

Speed v = Distance (s)/Time (t)

For a traveling sound wave, the distance between the source of a sound and the reflector is '2S'.

Speed v = 2 × distance (S)/Time (T)

V = 2S/t

2S = vt

Given speed of the wave = 342m/s

Distance covered = 450m

t = 2S/v

t = (2×450)/343

t = 900/343

t = 2.62seconds

It will take him 2.62seconds for him to hear his own voice echo off of the wall.

5 0
2 years ago
Read 2 more answers
Practice 3: Label the correct phase that would result from the Moon and Earth in these positions.
Anna71 [15]

Answer:

both position I think in nor

5 0
3 years ago
Read 2 more answers
A monster truck enters a freeway with a speed of 0 m/s and accelerates at a rate of 25 m/s2 in 5 seconds. How far does the car t
Furkat [3]

Answer:

312.5

Explanation:

we know that

s= ut + 1/2 at^2

= 0*5+1/2*25*5^2

= 0+ 625/2

=312.5

plz mark as brainalist

5 0
3 years ago
Explain what is happening when the girl is at each point. **The girl has started at 1 and goes to 4.
Shkiper50 [21]
Gravity
Is happening
5 0
2 years ago
Other questions:
  • Explain why the atomic mass of an element is a weighted-average mass
    6·1 answer
  • Is Their A Video On The Pysical Thingie
    8·1 answer
  • At a particular instant, a moving body has a kinetic energy of 295 J and a momentum of magnitude 25.1 kg · m/s.(a)What is the sp
    13·1 answer
  • A hot air balloon contains 85,000 moles of air. To what temperature must the
    8·1 answer
  • Which is not a metric base unit?
    6·1 answer
  • Can someone help me please
    12·1 answer
  • Please help!!
    12·1 answer
  • If a 5.5 kg object experiences 15 N of force for .15 seconds what is the speed change
    15·1 answer
  • The image shows devices that convert wind energy into electrical energy. What is one advantage of using this type of device in p
    11·1 answer
  • When Momentum is conserved it is called ________ .​
    11·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!