A motorist traveling at 45 km/h applies the brake so that the car decelerates uniformly at 4.0 m/s2. a. How far does the car travel during the 2.0 sec immediately after the brakes are applied? b. Find the car's velocity at the end of this 2.0-sec. time interval? c. What time is needed for the car to come to rest after the brakes are applied? d. Find the total distance the car travels while decelerating.
Displacement, Velocity and Acceleration
In classical mechanics, kinematics deals with the motion of a particle. It deals only with the position, velocity, acceleration, and displacement of a particle. It has no concern about the source of motion.
Linear Displacement
The term "displacement" refers to when something shifts away from its original "location," and "linear" refers to a straight line. As a result, “Linear Displacement” can be described as the movement of an object in a straight line along a single axis, for example, from side to side or up and down. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Non-contact sensors such as LVDTs and other linear location sensors can calculate linear displacement. Linear displacement is usually measured in millimeters or inches and may be positive or negative.
![### Motion and Deceleration in Vehicles
A motorist traveling at 45 km/h applies the brake so that the car decelerates uniformly at 4.0 m/s². Below are several questions concerning this scenario:
#### a. How far does the car travel during the 2.0 sec immediately after the brakes are applied?
To determine the distance traveled by the car during the first 2.0 seconds after brakes are applied, we can use the formula:
\[ \text{Distance} = v_i t + \frac{1}{2} a t^2 \]
where:
- \( v_i \) is the initial velocity,
- \( t \) is the time,
- \( a \) is the acceleration.
First, convert the initial velocity from km/h to m/s:
\[ v_i = 45 \, \text{km/h} \times \frac{1000 \, \text{m}}{1 \, \text{km}} \times \frac{1 \, \text{h}}{3600 \, \text{s}} = 12.5 \, \text{m/s} \]
Now, apply the values to the formula:
\[ d = (12.5 \, \text{m/s} \times 2.0 \, \text{s}) + \frac{1}{2} (-4.0 \, \text{m/s}^2 \times (2.0 \, \text{s})^2 ) \]
\[ d = 25.0 \, \text{m} + \frac{1}{2} (-16.0 \, \text{m}) \]
\[ d = 25.0 \, \text{m} - 8.0 \, \text{m} \]
\[ d = 17.0 \, \text{m} \]
So, the car travels **17.0 meters** in 2.0 seconds.
#### b. Find the car’s velocity at the end of this 2.0-sec time interval?
To find the velocity at the end of the 2.0-second interval, use the equation:
\[ v_f = v_i + a t \]
where:
- \( v_f \) is the final velocity,
- \( v_i \) is the initial velocity (12.5 m/s),
- \( a \) is the acceleration (-](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F49af36b6-1765-45ff-82e0-c4fa20ab1884%2F7a08bdd5-8cee-43ba-ac91-bdaebdcf6bd9%2F8oo14e_processed.png&w=3840&q=75)

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