A stuntman of mass 55 kg is to be launched horizontally out of a spring-

Zach runs a 100-meter race. 7 seconds after the race started Zach is 35 meters from the starting line and reaches his max speed;

Angelina_Jolie [31]

Answer:MaxSpeed=8 m/s. Additional distance during z seconds after top speed is 8*z meters. Now the distance at 7+z seconds after the race starts is D=( 35+8*z) meters. For x ≥ 7 the time of the race, then D=(35+(x-7)*8) meters is the distance traveled during that time.

Explanation:

First we are interested in calculating the top speed, that is constant. We know at 35 meters he reaches the top speed and this happens 7 seconds after the race started. Also he is at 75 meters from the starting line 12 seconds after the beginning, then we can use the definition of speed, in this case is constant, to get its value: Speed=change in distance / change in time

Then Speed= (75-35)meters/(12-7)seconds = 40m/5s=8m/s. That is the topspeed=8 m/s

Now from the 35 meters he runs at constant speed, then if we are told he runs z seconds and we are asked the distance he runs in that time, we know the distance at constant speed is D=V*t,

then D= 8m/s * z seconds=8z meters.

But here since the run is a 100 meters-race we have an upper bound for z, here he has left (100-35)=65 meters to run at 8m/s, then he can maximum run additional 8,125 second or 15,125 seconds in total for the race.

That is D=8*z meters, with z < 8,125 seconds, this is the additional distance he can run after reaching his top speed.

Now the distance at 7+z seconds after the race starts is D=( 35+8*z) meters, the first 35 m he runs until reaching his top speed and the rest of the distance at this speed.

for x the total time of the run at a given point, we are asked the distance he has traveled at that time, then we are also told x ≥ 7, then D=(35+(x-7)*8) meters, we subtract the 7 initial seconds because they are already counted in the initial 35 meters.

7 0

4 years ago

A student on a skateboard is moving at a speed of 1.40 m/s at the start of a 2.15 m high and 12.4 m long incline. The total mass

saw5 [17]

Answer:

W = 609.97J

Explanation:

In order to calculate the work done by the student, you take into account that the total work is equal to the change of the kinetic energy of the student, as follow:

$W_T=\Delta K\\\\W+W_g-W_f=\frac{1}{2}m(v^2-v_o^2)\\\\W+Mgsin\alpha d-F_fd=\frac{1}{2}m(v^2-v_o^2)$ (1)

The work done by the friction force is negative because it is against the motion of the student.

W: work done by the student = ?

Wf: work done by the friction force

Wg: work done by the gravitational force

Ff: total friction force = 41.0N

m: mass of the skateboard = 53.0kg

d: distance traveled by the student

v: final speed of the student = 6.90m/s

vo: initial speed of the student = 1.40m/s

α: angle of the incline

You first calculate the distance d, with the Pythagoras' theorem

$d=\sqrt{(2.15m)^2+(12.4m)^2}=12.58m$

Furthermore, the angle α is:

$\alpha=tan^{-1}(\frac{2.15m}{12.4m})=9.83\°$

Then, you solve the equation (1) for W and replace the values of all parameters:

$W=\frac{1}{2}m(v^2-v_o^2)+F_fd-Mgsin\alpha d\\\\W=\frac{1}{2}(53.0kg)((6.90m/s)^2-(1.40m/s)^2)+(41.0N)(12.58m)\\-(53.0kg)(9.8m/s^2)sin(9.83\°)(12.58m)\\\\W=609.97J$

The work done by the student is 609.97J

6 0

4 years ago

Describing motion using words instead of numbers is called ....... kinematics??

Aleksandr [31]

Translational kinematics

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High-frequency sound waves have a shorter (amplitude, pitch, wavelength) and a higher (amplitude, pitch, wavelength) than low-fr

I am Lyosha [343]

The most appropriate answers are ...

high frequency sound has shorter wavelength !

a higher pitch than low frequency...!!

so , wavelength and pitch !!

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In order to meet the demands for new matter, what must Earth’s residents do?

loris [4]

I think the correct answer from the choices listed above is the second option. <span>In order to meet the demands for new matter, Earth's resident must recycle the available matter. Hope this answers the question. Have a nice day.</span>

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3 years ago

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