Question

What was the initial speed of a car if its speed is 40 m/s after 5 seconds of accelerating at -4 m/s2? A. 20 m/s B. 50 m/s C. 60 m/s D. 25 m/s

Answer 1

The initial speed of the car was 60 m/s, found by rearranging and substituting values into the kinematic equation for uniformly accelerated linear motion.

Step-by-step explanation:

The initial speed of a car can be determined using the equation of motion that relates initial velocity, acceleration, and time to final velocity. The final velocity (v) is given as 40 m/s, the acceleration (a) is -4 m/s2 indicating deceleration, and the time (t) is 5 seconds. Using the formula v = u + at, where u is the initial velocity, we can rearrange the equation to solve for u: u = v - at.

Plugging in the known values, we get:

u = 40 m/s - (-4 m/s2 × 5 s) = 60 m/s.

Therefore, the initial speed of the car was 60 m/s.

Answer 2

Hmm 70m/s per hour....