Answer:
The ground pushes back on your feet with equal force
Explanation:
When you walk across the ground and push on it with your feet, the ground pushes back on your feet with an equal and opposite force.
This interpretation and knowledge is gotten from Newton's third law of motion.
It states that "action and reaction force are equal and opposite in nature".
- The force applied to a body responds with an opposite force in the other direction.
- Therefore, the reaction force is of equal magnitude but directed in another direction.
Answer:
a) It reduces the kinetic energy loss of the stunt person.
Answer: B
Explanation:
X-rays coming into Earth's system from space are absorbed by the atmosphere. Telescopes that processes X-rays, therefore, are placed in orbit above the atmosphere
Answer: depth = 3.75 m
Explanation:
Taken the speed of the sound in sea to be V = 1500 m/s
The time between an echo sounder sending and receiving a pulse is 0.005 s. That is,
Total time T = 0.005
Formula for echo is:
V = 2X/T
Where X = distance covered
Substitute V and T into the formula
1500 = 2X/0.005
Cross multiply
7.5 = 2X
Make X the subject of formula
X = 7.5/2
X = 3.75 m
Therefore, the depth of the sea is 3.75 m
Answer:at 21.6 min they were separated by 12 km
Explanation:
We can consider the next diagram
B2------15km/h------->Dock
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B1 at 20km/h
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V
So by the time B1 leaves, being B2 traveling at constant 15km/h and getting to the dock one hour later means it was at 15km from the dock, the other boat, B1 is at a distance at a given time, considering constant speed of 20km/h*t going south, where t is in hours, meanwhile from the dock the B2 is at a distance of (15km-15km/h*t), t=0, when it is 8pm.
Then we have a right triangle and the distance from boat B1 to boat B2, can be measured as the square root of (15-15*t)^2 +(20*t)^2. We are looking for a minimum, then we have to find the derivative with respect to t. This is 5*(25*t-9)/(sqrt(25*t^2-18*t+9)), this derivative is zero at t=9/25=0,36 h = 21.6 min, now to be sure it is a minimum we apply the second derivative criteria that states that if the second derivative at the given critical point is positive it means here we have a minimum, and by calculating the second derivative we find it is 720/(25 t^2 - 18 t + 9)^(3/2) that is positive at t=9/25, then we have our answer. And besides replacing the value of t we get the distance is 12 km.
