Please help, i tried twice already.
What is the acceleration of an object if it goes from a velocity of +25 m/s to rest in 5.0 s?

A.
–5 m/s2

B.
+5 m/s2

C.
–25 m/s2

D.
+25 m/s2

Question

Please help, i tried twice already.
What is the acceleration of an object if it goes from a velocity of +25 m/s to rest in 5.0 s?	
 
 A.
–5 m/s2
 
 B.
+5 m/s2
 
 C.
–25 m/s2
 
 D.
+25 m/s2

anonymous · Answer

$$v(t)=v_o+at$$
$$v(5)=0$$
$$0 = 25 + a \times 5$$
$$5a = -25$$
$$a = -5_{m/s^2}$$

jim_thompson5910 · Answer

Go here http://www.studyphysics.ca/newnotes/20/unit01_kinematicsdynamics/chp04_acceleration/lesson11.htm scroll down to where it says `"How to Choose the Right Formula!"` (almost near the bottom) you'll find this table http://www.studyphysics.ca/newnotes/20/unit01_kinematicsdynamics/chp04_acceleration/images/formulas.GIF it says `"To choose the correct formula, look for the one thing that you are not given or asked for as the 'missing' part of a formula."` We're not given the distance and we don't want to find the distance. So we look for an X under the d column and we find that we have to use this formula $$\Large V_{f} = V_{i} + a*t$$

jim_thompson5910 · Answer

In this case,

$$\Large V_{f} = 0, \ V_{i} = 25, \ t = 5$$