Answer:
t = 3 seconds
Explanation:
Given that,
Initial speed, u = 30 m/s
Final speed, v = 0
It slides 45 m to rest.it take the box to come to rest
We need to find how long it take the box to come to rest.
Let a be the acceleration and t is time.

Now finding time.

So, the required time is 3 seconds.
Answer:39.88 rad/s
Explanation:
Given
mass of cylinder m_1=18 kg
radius R=1.7 m
angular speed 
mass of
dropped at r=0.3 m from center
let
be the final angular velocity of cylinder
Conserving Angular momentum





A force is a push or pull acting upon an object as a result of its interaction with another object. There are a variety of types of forces. a variety of force types were placed into two broad category headings on the basis of whether the force resulted from the contact or non-contact of the two interacting objects.
Contact Forces
Action-at-a-Distance Forces
Frictional Force
Gravitational Force
Tensional Force
Electrical Force
Normal Force
Magnetic Force
Air Resistance Force
Applied Force
Spring Force
These are types of individual forces
Applied Force
Gravitational Force
Normal Force
Frictional Force
Air Resistance Force
Tensional Force
Spring Force
As the metal expands as does the road bed so neither really effevts those foing over the bridge. as it is hot the metal will expand and so will most tarmac on roads.