Homework Help: physics

Posted by Taylor on Monday, September 6, 2010 at 9:52pm.

A car starts from rest and travels for 4.9 s with a uniform acceleration of +1.8 m/s2. The driver then applies the brakes, causing a uniform acceleration of -1.7 m/s2. The breaks are applied for 1.50 s.
1) How fast is the car going at the end of the breaking period?
2) How far has the car gone from its start?

physics - bobpursley, Monday, September 6, 2010 at 10:04pm
Lets look at momentum.

The impulse equation ought to equal the final momentum.

F1*time1+F2*time2=mass*vfinal
but Force= mass*acceleration.
mass*1.8*4.9-mass*1.7*1.5= mass*Vfinal
solve for Vfinal.

How far?
distance= avg velocity*time
= Vf/2 * (1.5+4.9)

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