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3 years ago

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In a race, Usain bolt accelerates at 1.99 m/s^2 for the first 60.0 m, then decelerates at -0.266 m/s^2 for the final 40.0 m. How

much time did the race take?

1 answer:

GalinKa [24]3 years ago

6 0

7 miles long i think bc i dont know bc i am bad at math and math is good

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2. A 2000 kg car with speed 12.0 m/s hits a tree. The tree does not move or

krek1111 [17]

a) The work done by the tree is $-1.44\cdot 10^5 J$

b) The amount of force applied is 2880 N

Explanation:

a)

According to the work-energy theorem, the work done on the car is equal to the change in kinetic energy of the car. Therefore, we can write:

$W=K_f - K_i = \frac{1}{2}mv^2 - \frac{1}{2}mu^2$

where

W is the work done on the car

m is the mass of the car

u is its initial speed

v is its final speed

For the car in this problem, we have:

m = 2000 kg

u = 12.0 m/s

v = 0 (since the car comes to a stop, after the crash)

Therefore, the work done by the tree on the car is:

$W=0-\frac{1}{2}(2000)(12.0)^2=-1.44\cdot 10^5 J$

The work is negative because it is done in the direction opposite to the direction of motion of the car.

b)

The work done by the tree on the car can also be rewritten as

$W=Fd$

where

F is the force applied on the car

d is the displacement of the car during the collision

In this situation, we have:

$W=-1.44\cdot 10^5 J$ is the work done

$d=50.0 cm = 0.50 m$ is the displacement of the car during the collision

Solving the equation for F, we find the force exerted by the tree on the car:

$F=\frac{W}{d}=\frac{-1.44\cdot 10^5 J}{0.50}=-2880 N$

Where the negative sign means the force is applied opposite to the direction of motion of the car. Therefore, the magnitude of the force applied is 2880 N.

Learn more about work:

brainly.com/question/6763771

brainly.com/question/6443626

#LearnwithBrainly

3 0

4 years ago

find out how was life like in ancient China by exploring the engineering and metal technology of Ancient China. Gather some poin

scZoUnD [109]

The grand canal was built to make easier the transportation of grains to the power center of north china.

<h3>How was the Grand Canal built?</h3>

The canal was built in order to connect the Yellow River in the north with the Yangtze River in the south. This canal is built for making easier the transportion of grain from the south to the centers of north China. The total length of the Grand Canal is 1,776 km.

So we can conclude that the grand canal was built to make easier the transportation of grains to the power center of north china.

Learn more about technology here: brainly.com/question/25110079

5 0

2 years ago

Please help me with physics homework I just need help with C and D. Picture is included

marysya [2.9K]

Answer:

For C is B and for D is A

Explanation:

B because that's where the b car will do all the force to go up, and A because there the car doesn't have to do any force other than the natural, and it already brings that on it's own.

5 0

4 years ago

What is the critical angle and how does it relate to total internal reflection?

liubo4ka [24]

Answer:

critical angle is the angle of incidence in optically denser medium, for which the angle of reflection in the less denser medium is 90 degree

Explanation:

total internal reflection occurs at one particular angle of incidence where the reflected ray lies on the boundary.

this angle is called the critical angle

6 0

3 years ago

On august 10, 1972, a large meteorite skipped across the atmosphere above the western united states and western canada, much lik

RUDIKE [14]

(a)
The velocity of the meteorite just before hitting the ground is:
$v=20 km/s=20000 m/s$
The loss of energy of the meteorite corresponds to the kinetic energy the meteorite had just before hitting the ground, so:
$\Delta K = \frac{1}{2}mv^2= \frac{1}{2}(3.4 \cdot 10^6 kg)(20000 m/s)^2=6.8 \cdot 10^{14}J$

(b) 1 megaton of tnt is equal to $1 MT=4.2 \cdot 10^{15}J$
To find to how many megatons the meteorite energy loss $\Delta E$
corresponds, we can set the following proportion
$1 MT: 4.2 \cdot 10^{15}J=x: \Delta E$
And so we find
$x= \frac{\Delta E}{4.2 \cdot 10^{15}J} = \frac{6.8 \cdot 10^{14}J }{4.2 \cdot 10^{15}J} =0.162 MT$
So, 0.162 megatons.

(c) 1 Hiroshima bomb is equivalent to 13 kilotons (13 kT). The impact of the meteorite had an energy of $\Delta E=0.162 MT=162 kT$ . So, to find to how many hiroshima bombs it corresponds, we can set the following proportion:
$1:13 kT=x:162 kT$
And so we find
$x= \frac{162 kT}{13 kT}=12.46$
So, the energy released by the impact of the meteorite corresponds to the energy of 12.46 hiroshima bombs.

7 0

4 years ago