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andrey2020 [161]
3 years ago
5

Jessica Jacob is driving down the road at 35 m/s. She sees a cop and slows to 20 m/s in only 2 seconds. What was her acceleratio

n?
Physics
1 answer:
kati45 [8]3 years ago
8 0

Answer: Acceleration = - 7.5 m/s^2

Explanation:

Acceleration (a) is the rate of change in velocity. I.e

Acceleration = (V - U)/t

U = 35 m/s

V = 20 m/a

t = 2 s

Acceleration = ( 20 - 35 )/2

Acceleration = - 15/2

Acceleration = - 7.5 m/s^2

In this case, the car is decelerating at 7.5 m/s^2

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sketch a graph of position vs. time for a person starting 0.4 m away and standing still. Include an explanation of your predicti
Korvikt [17]

Answer:

Straight line parallel to time axis.

Explanation:

The slope of the position time graph gives the velocity.

As the man is still, that means the velocity is zero. So, the slope of the graph is zero. It is a straight line parallel to time axis.

5 0
3 years ago
Train cars are coupled together by being bumped into one another. Suppose two loaded cars are moving toward one another, the fir
tia_tia [17]

Answer:

7560 Joules

Explanation:

m_1 = Mass of first car = 1.5\times 10^5\ kg

m_2 = Mass of second car = 2\times 10^5\ kg

u_1 = Initial Velocity of first car = 0.3 m/s

u_2 = Initial Velocity of second car = -0.12 m/s

v = Velocity of combined mass

As linear momentum of the system is conserved

m_1u_1 + m_2u_2 =(m_1 + m_2)v\\\Rightarrow v=\frac{m_1u_1 + m_2u_2}{m_1 + m_2}\\\Rightarrow v=\frac{1.5\times 10^5\times 0.3 + 2\times 10^5\times -0.12}{1.5\times 10^5 + 2\times 10^5}\\\Rightarrow v=0.06\ m/s

Energy lost is

\Delta E=\Delta E_i-\Delta E_f\\\Rightarrow \Delta=\frac{1}{2}(m_1u_1^2 + m_2u_2^2-(m_1+m_2)v^2)\\\Rightarrow \Delta=\frac{1}{2}(1.5\times 10^5\times 0.3^2 + 2\times 10^5\times (-0.12)^2-(1.5\times 10^5 + 2\times 10^5)\times 0.06^2)\\\Rightarrow \Delta=7560\ J

The Energy lost in the collision is 7560 Joules

7 0
3 years ago
Can a goalkeeper at his goal kick a soccer ball into the opponent’s goal without the ball touching the ground? The distance will
zmey [24]

The goalkeeper at his goal cannot kick a soccer ball into the opponent’s goal without the ball touching the ground

Explanation:

Consider the vertical motion of ball,

We have equation of motion v = u + at

     Initial velocity, u  = u sin θ

     Final velocity, v =  0 m/s    

     Acceleration = -g

     Substituting

                      v = u + at  

                      0 = u sin θ - g t

                      t=\frac{usin\theta }{g}

This is the time of flight.

Consider the horizontal motion of ball,

        Initial velocity, u =  u cos θ

        Acceleration, a =0 m/s²  

        Time, t=\frac{usin\theta }{g}  

     Substituting

                      s = ut + 0.5 at²

                      s=ucos\theta \times \frac{usin\theta }{g}+0.5\times 0\times (\frac{usin\theta }{g})^2\\\\s=\frac{u^2sin\theta cos\theta}{g}\\\\s=\frac{u^2sin2\theta}{2g}

This is the range.

In this problem

              u = 30 m/s

              g = 9.81 m/s²

              θ = 45° - For maximum range

Substituting

               s=\frac{30^2\times sin(2\times 45)}{2\times 9.81}=45.87m

Maximum horizontal distance traveled by ball without touching ground is 45.87 m, which is less than 95 m.

So the goalkeeper at his goal cannot kick a soccer ball into the opponent’s goal without the ball touching the ground

6 0
4 years ago
Which of the following types of radiation can penetrate through paper but not through wood?
andrew-mc [135]
The type of radiation that can penetrate through paper, but not through wood is called beta rays. Beta rays can penetrate paper and air, but a thin piece of alimony can stop it. Gamma can cut through anything except lead and many inches of concrete. Alpha can be stopped by paper and not penetrated. The correct answer is B.
4 0
3 years ago
Read 2 more answers
Give an example of how electrical energy and thermal energy are connected.
mafiozo [28]
A toaster draws electric current (electrical energy) from a wall outlet and converts these moving electric charges into heat (thermal energy) in the filaments that turn red hot to cook your toast. ... As electricity runs through the filaments in a space heater, the electrical energy is converted into heat (thermal energy).
Hopefully this helped.
3 0
4 years ago
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