The answer to the blank above is 20. The speed limit given provided that you cannot see the tracks for 400 ft in both directions is always 20 mph. Basically, this 20 mph is decided based upon the traffic laws in order to avoid road casualties. Since it is "uncontrolled railroad crossing", the minimum speed should be implemented to slow down for the purpose of traffic calming measures. Other than this, the 20 mph is also applicable in narrowing roads as well as speed humps.
The time is given, and you want to find the average velocity. To do this, you need to know the distance covered by the driver around the racetrack in that 30 seconds. You divide this by the time, then you will obtain the average velocity in units of, say meters per second.
Answer:twice of initial value
Explanation:
Given
spring compresses 
distance for some initial speed
Suppose v is the initial speed and k be the spring constant
Applying conservation of energy
kinetic energy converted into spring Elastic potential energy
When speed doubles
divide 1 and 2
Therefore spring compresses twice the initial value
The answers would be:
CONVERGENT boundary - Crust submerges into the mantle
TRANSFORM boundary - neither forms nor submerges
DIVERGENT boundary - new crust forms
If you'd like to know more about the different boundaries, read on:
Convergent boundaries occur when two plates move TOWARDS each other. The event where crust submerges into the mantle is called <em><u>subduction</u></em> and this occurs when an oceanic plate and a continental plate collide. The oceanic plate is more dense and thinner than the continental plate, so it slides under it.
Transform boundaries occur when two plates slide against each other. They move slide side by side, so nothing is formed nor do they go under each other. Although, this type of boundaries create strong earthquakes.
Lastly, divergent boundaries occur when two plates move apart. The separation creates a way for magma to come up. New crust is formed when the magma that seeps out is cooled by its cooler surroundings. This is observed in the mid oceanic ridge.
The work done is the product between the intensity of the force applied F, the amount of the displacement d of the book and the cosine of the angle
between the direction of the force and the direction of the displacement:
In our problem, the student is lifting the book, so he is applying a force directed upward, and the book is moving upward, so F and d are parallel and therefore the angle is zero, so
Therefore, the work done is
