lemer785
Answered

A car starting from rest has a constant acceleration of 4 meters per second per second. How long will it take to reach a speed of 20 m/s?

A. 1.25 sec
B. 4 sec
C. 5 sec
D. 20 sec



Answer :

To determine how long it will take for a car starting from rest to reach a speed of 20 meters per second with a constant acceleration of 4 meters per second squared, we can use the first equation of motion:

[tex]\[ v = u + at \][/tex]

where:
- [tex]\( v \)[/tex] is the final velocity (20 m/s in this case),
- [tex]\( u \)[/tex] is the initial velocity (0 m/s since the car starts from rest),
- [tex]\( a \)[/tex] is the acceleration (4 m/s²),
- [tex]\( t \)[/tex] is the time we need to find.

Step-by-step, it works as follows:

1. Plug in the known values:
[tex]\[ 20 = 0 + 4t \][/tex]

2. Simplify the equation:
[tex]\[ 20 = 4t \][/tex]

3. Solve for [tex]\( t \)[/tex] by dividing both sides by 4:
[tex]\[ t = \frac{20}{4} \][/tex]

4. This gives:
[tex]\[ t = 5 \text{ seconds} \][/tex]

Thus, it will take the car 5 seconds to reach a speed of 20 m/s. Therefore, the correct answer is:

5 sec