Question

100 point question!! A driver begins to brake when her car is traveling at 15.0 m/s, and the car comes to a stop 4.0 s later. How much farther does the car go after the driver begins to brake, assuming constant acceleration?

Answer 1

Answer:

30 m

Explanation:

Let's list out the known variables that we are given in this question.

• v₀ = 15 m/s
• v = 0 m/s
• t = 4 s

We are trying to solve for displacement in the x-direction.

• Δx = ?

Find which constant acceleration equation contains all 4 of these variables.

• $\displaystyle \triangle x = \Big (\frac{v+v_0}{2} \Big ) t$

Plug the known values into the equation and solve for delta x.

• $\displaystyle \triangle x = \Big (\frac{0+15}{2} \Big ) \cdot 4$
• $\displaystyle \triangle x = \Big (\frac{15}{2} \Big ) \cdot 4$  
• $\displaystyle \triangle x =\frac{60}{2}$
• $\triangle x = 30$

The car goes 30 m after the driver begins to brake.