Answer:
a. 
b.
must be the minimum magnitude of deceleration to avoid hitting the leading car before stopping
c.
is the time taken to stop after braking
Explanation:
Given:
- speed of leading car,

- speed of lagging car,

- distance between the cars,

- deceleration of the leading car after braking,

a.
Time taken by the car to stop:

where:
, final velocity after braking
time taken


b.
using the eq. of motion for the given condition:

where:
final velocity of the chasing car after braking = 0
acceleration of the chasing car after braking

must be the minimum magnitude of deceleration to avoid hitting the leading car before stopping
c.
time taken by the chasing car to stop:


is the time taken to stop after braking
Answer:
2s
Explanation:
Given parameters:
Distance = 30m
Speed = 15m/s
Unknown:
Time before Laurence caught it = ?
Solution:
To solve this problem;
Speed =
Time taken =
=
= 2s
The time it takes is 2s
Answer:
C). 
Explanation:
As we know that capacitance of a given capacitor is

now we know that energy stored in the capacitor plates

here if all the dimensions of the capacitor plate is doubled
then in that case

here area becomes 4 times on doubling the radius and the distance between the plates also doubles
So new capacitance is now

so capacitance is doubled
now the final energy stored between the plates of capacitor is given as

so the final energy is


The object is moving, so at different times, it has different displacement. I'm guessing that you probably want to know the displacement at the end of the time on the graph ... 5 seconds.
Displacement is the distance and the direction FROM (the position at the beginning) TO (the position at the end).
At the beginning ... time=0 ... the position is 1 meter.
At the end ... time=5 ... the position is zero.
The distance FROM the beginning TO the end is (zero - 1m) . That's <em>-1m </em>.