Answer to Question #277461 in Physics for Ahmrii

Question

The driver of a 2.0 × 103 kg red car traveling on the highway at 45m/s slams on

his brakes to avoid striking a second yellow car in front of him, which had come

to rest because of blocking ahead as shown in above Fig. After the brakes are

applied, a constant friction force of 7.5 × 103 N acts on the car. Ignore air

resistance.

(a) Determine the least distance should the brakes be applied to avoid a

collision with the other vehicle?

(b) If the distance between the vehicles is initially only 40.0 m, at what speed

would the collision occur?

(c) Write your conclusive observations on the result obtained from this

numerical. I.e. the importance of Physics in daily life.

Solution

3

3

:

2.0 10

45 /

7.5 10

Given data in this Question

mass of the car is kg

velocity of the car is u m s

final velocity v

Friction force is kg

 

 

 

 

Answer 1

(a)

$$d=v^2/(2a)=v^2/(2·F/m)=270\text{ m}.$$

(b)

$$v_f=\sqrt{v^2-2xa}=\sqrt{v^2-2xF/m}=42\text{ km/h}.$$

(c) Physics gives us the values that will save our lives on roads.