Answer:
0.22 m
Explanation:
We are told that the driver can survive an acceleration of 50g only if the collision lasts no longer than 30 ms. So,

The acceleration is

where the negative sign is due to the fact that this is a deceleration, since the driver comes to a stop in the collision.
First of all, we can find what the initial velocity of the car should be in this conditions by using the equation:

And since the final velocity is zero, v=0, and solving for u,

And now we can find the corresponding distance travelled using the equation:

Answer:

Explanation:
For the first ball, the moment of inertia and the kinetic energy is:


So, replacing, we get that:

At the same way, the moment of inertia and kinetic energy for second ball is:


So:

Then,
is equal to
, so:




Finally, solving for
, we get:

Answer:
1. The force of the shelf holding the book up.
Explanation:
The free body diagram of the book is as follows:
1 - The weight of the book towards downwards
2 - The normal force that the shelf exerts on the book towards upwards.
Since the book is at rest, these two forces are equal to each other and according to Newton's Third Law the reaction force to the force of gravity is equal but opposite to the weight of the book. This reaction force is the one that holds the book up on the shelf.
You will have to use this formula:

Final Velocity (V) = 4m/s
Initial Velocity (Vo) = 8m/s
Acceleration (a) = ? m/s^2
Time (t) = 2 secs
Then:
-> 4 = 8 + a x 2
-> 4 - 8 = 2a
-> -4 = 2a
-> a = -4/2
-> a = -2 m/s^2
Ps: It's value is negative because the she was in retrograde motion.
Answer: Her acceleration is -2 m/s^2.
the answer could be (very basic) since options arent given