Ask question

Ask question

All categories

3 years ago

8

You are traveling on an interstate highway at the posted speed limit of 70 mph when you see that the traffic in front of you has

stopped due to an accident up ahead. You step on your brakes to slow down as quickly as possible. Assume that you to slow down to 30 mph in about 5 seconds. A) With this same average acceleration, how much longer would it take you to stop?
B) What total distance would you travel from when you first apply the brakes until the car stops?

1 answer:

vovikov84 [41]3 years ago

3 0

Answer:8.75 s,

136.89 m

Explanation:

Given

Initial velocity $=70 mph\approx 31.29 m/s$

velocity after 5 s is $30 mph\approx 13.41 m/s$

Therefore acceleration during these 5 s

$a=\frac{v-u}{t}$

$a=\frac{13.41-31.29}{5}=-3.576 m/s^2$

therefore time required to stop

v=u+at

here v=final velocity =0 m/s

initial velocity =31.29 m/s

$0=31.29-3.576\times t$

$t=\frac{31.29}{3.576}=8.75 s$

(b)total distance traveled before stoppage

$v^2-u^2=2as$

$0^2-31.29^2=2\times (-3.576)\cdot s$

s=136.89 m

You might be interested in

Someone please help me!! See PDF to help

Mama L [17]

Answer:

They are invisible!

Explanation:

5 0

3 years ago

Read 2 more answers

viewed from earth two stars form an angle of 76.04 degrees. StarA is 23.30 light years from earth star Bis 34.76 light years fro

kirill115 [55]

The observation point on Earth and the two stars form a triangle. The two sides of the triangle are 23.3 ly and 34.76 ly and their included angle is 76.04°. We can use the cos rule to find the third side, which is the distance between the two stars.
c² = a² + b² - 2abCos(C)
c² = (23.3)² + (34.76)² - 2(23.3)(34.76)Cos(76.04)
c = 36.88 light years.

4 0

3 years ago

3. A worker pushes a box across the floor to the right at a constant speed with a force of 25N. What

WITCHER [35]

Answer:

Friction between the box and the floor is 25N to the left.

Explanation:

According to Newton's second law of motion, the net force acting on an object is equal to the produce between the object's mass and its acceleration:

$F_{net}=ma$

where

m is the mass of the object

a is its acceleration

In this problem, we have two forces acting on the object:

- The applied force, F = 25 N, to the right

- The force of friction $F_f$ , opposing the motion of the box, so to the left

So we can write the net force as

$F_{net}=F-F_f$

Also, we know that the box is moving at constant speed: this means its acceleration is zero, so

$a=0$

Therefore

$F_{net}=0$

WHich means:

$F-F_f=0$

And therefore,

$F_f=F=25 N$

which means that the force of friction is also 25 N.

6 0

3 years ago

Due Sun 06/09/2019 11:59 pm Skip Navigation Questions correct Q 1 [1/1] correct Q 2 [1/1] correct Q 3 [1/1] untried Q 4 (0/1) un

astraxan [27]

Due Sun 06/09/2019 11:59 pm <u><em>(you're already more than a week late)</em></u> Skip Navigation Questions, correct Q 1 [1/1], correct Q 2 [1/1], correct Q 3 [1/1], untried Q 4 (0/1), untried Q 5 (0/1), untried Q 6 (0/1), untried Q 7 (0/1), untried Q 8 (0/1), untried Q 9 (0/1), untried Q 10 (0/1), Grade: 3/10, Print Version, <u><em>Start of Questions</em></u>:

Questions Two cyclists, 42 miles apart, start riding toward each other at the same time. One cycles 2 times as fast as the other. If they meet 2 hours later, what is the speed (in mi/h) of the faster cyclist?

<u><em>Start of Answer:</em></u>

-- When they started, they were 42 miles apart. When they met, 2 hours later, they were no miles apart. The distance between them shrank at the rate of 21 miles per hour. Since they rode directly toward each other, the sum of their individual speeds must have been 21 miles per hour.

-- One biker was two times the speed of the other. Slower biker: 1 time. Faster biker: 2 times. Sum of their speeds: 3 times = 21 miles per hour. Each 'time' = 7 miles per hour.

-- Slower cycler = 1 time = 7 mi/hr

<em>Faster cycler = 2 times = 14 mi/hr</em>

5 0

3 years ago

1. A 0.40 kg ball is launched at a speed of 16 m/s from a 22 m cliff.

Masja [62]

Answer:

51.2 J, 86.2 J, 137.4 J

Explanation:

The kinetic energy of the ball is given by:

$K=\frac{1}{2}mv^2$

where

m = 0.40 kg is its mass

v = 16 m/s is its speed

Substituting,

$K=\frac{1}{2}(0.40)(16)^2=51.2 J$

The potential energy of the ball is given by

$U=mgh$

where

m = 0.40 kg

$g=9.8 m/s^2$ is the acceleration of gravity

h = 22 m is the heigth of the cliff

Substituting,

$U=(0.40)(9.8)(22)=86.2 J$

Finally, the total mechanical energy is the sum of the kinetic energy and the potential energy:

$E=K+U=51.2 + 86.2=137.4 J$

4 0

3 years ago