Answer:
a) The flea's speed when it leaves the ground is 
b) The flea move
upward while it is pushing off
Explanation:
Hi
<u>Knwons</u>
Mass
, Work
and Force 
a) Here we are going to use
, so 
a) Here we are going to use
, so
or
approx.
yes she is very safe inside
Part a
Answer: NO
We need to calculate the distance traveled once the brakes are applied. Then we would compare the distance traveled and distance of the barrier.
Using the second equation of motion:

where s is the distance traveled, u is the initial velocity, t is the time taken and a is the acceleration.
It is given that, u=86.0 km/h=23.9 m/s, t=0.75 s, 

Since there is sufficient distance between position where car would stop and the barrier, the car would not hit it.
Part b
Answer: 29.6 m/s
The maximum distance that car can travel is 
The acceleration is same, 
The final velocity, v=0
Using the third equation of motion, we can find the maximum initial velocity for car to not hit the barrier:

Hence, the maximum speed at which car can travel and not hit the barrier is 29.6 m/s.
1) The mass of the continent is 
2) The kinetic energy of the continent is 1683 J
3) The speed of the jogger must be 6.57 m/s
Explanation:
1)
The continent can be represented as a slab of size

and depth

So its volume is

We also know that the density of the continent is

Therefore, we can calculate its mass as:

2)
The kinetic energy of the continent is given by

where
m is its mass
v is its speed
We have already calculate its mass, while the speed is
v = 3.2 cm/year
We have to convert into SI units first, as follows:

The mass is

So, the kinetic energy of the continent is

3)
Here we have a jogger having the same kinetic energy of the continent, so

And the kinetic energy of the jogger can be expressed as

where
m = 78 kg is the mass of the jogger
v is his speed
We can therefore re-arrange the equation to find the speed of the man, and we get:

Learn more about kinetic energy:
brainly.com/question/6536722
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