196k views
5 votes
Large cockroaches can run as fast as 1.50 m/s in short bursts. suppose that you turn on the light in a cheap motel and see a cockroach scurrying away from you in a straight line at a constant 1.50 m/s as you move toward it at 0.70 m/s. if you start 0.75 m behind it, what minimum constant acceleration would you need to catch up with the cockroach when it has traveled 1.30 m, just short of safety under a counter?

User Semloh
by
7.2k points

2 Answers

3 votes

Final answer:

To catch up with a cockroach that scurries away at 1.50 m/s while you approach it at 0.70 m/s, the minimum constant acceleration you need to achieve over a total distance of 2.05 m (accounting for your initial speed) in the time it takes for the cockroach to travel 1.30 m is 2.00 m/s².

Step-by-step explanation:

The question involves a scenario where you need to calculate the minimum constant acceleration required to catch up with a cockroach. First, we need to find out how long it takes for the cockroach to cover the 1.30 m distance. Since the cockroach's speed is constant (1.50 m/s), we can find the time (t) using the formula:

distance = speed × time
1.30 m = 1.50 m/s × t

So, t = 1.30 m / 1.50 m/s = 0.867 s.

You start 0.75 m behind and approach the cockroach at 0.70 m/s, so in that time, you will cover:

distance = speed × time
= 0.70 m/s × 0.867 s
= 0.608 m

You need to cover not just the 0.75 m you start behind, but also an additional 1.30 m the cockroach travels. So you need to cover 2.05 m total (1.30 m + 0.75m - 0.608m), but since you are already moving at 0.70 m/s, the actual distance you need to 'accelerate' across is:

2.05 m - 0.608 m = 1.442 m

Let's denote the required acceleration as 'a'. To find this acceleration, we can use the kinematic equation:

d = v₀t + 0.5at²

Where 'd' is the distance to accelerate across (1.442 m), 'v₀' is your initial velocity (0.70 m/s), and 't' is the time calculated earlier (0.867 s). Rearranging the equation for 'a', we get:

a = (2(d - v₀t)) / t²
= 2(1.442 m - (0.70 m/s × 0.867 s)) / (0.867 s)²
= 2.00 m/s²

Therefore, the minimum constant acceleration needed is 2.00 m/s².

User D K
by
8.2k points
3 votes
In order to catch up with the cockroach, the time it took for it to reach just before under the counter must be the same time for me to travel its covered distance. Thus,

time of cockroach = time of my motion
Time of cockroach = Distance/Constant Speed = 1.30 m/1.50 m/s = 0.867 seconds

We use this for the equation below:
x = v₀t + 0.5at²
0.75 m = (0.7 m/s)(0.867 s) + 0.5(a)(0.867 s)²
Solving for a,
a = 0.381 m/s²
User Lindsey
by
7.8k points