Question

question 6 (1 point)
a car traveling 60 km/h accelerates at the rate of 2.0 m/s2. how much time is required for the car to reach a speed of 90 km/h?
15 s
30 s
45 s
4.2 s

Explanation:

Step1: Convert the speeds to m/s

The initial speed \(v_0 = 60\ km/h=\frac{60\times1000}{3600}\ m/s=\frac{50}{3}\ m/s\approx16.67\ m/s\)
The final speed \(v = 90\ km/h=\frac{90\times1000}{3600}\ m/s = 25\ m/s\)
The acceleration \(a=2.0\ m/s^2\)

Step2: Use the kinematic equation \(v = v_0+at\)

We want to find \(t\), so we can re - arrange the equation to \(t=\frac{v - v_0}{a}\)
Substitute the values: \(t=\frac{25-\frac{50}{3}}{2}\)
First, calculate \(25-\frac{50}{3}=\frac{75 - 50}{3}=\frac{25}{3}\)
Then \(t=\frac{\frac{25}{3}}{2}=\frac{25}{6}\approx4.2\ s\)

Answer:

4.2 s