# average force question

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#### ssiding

##### Full Member
10+ Year Member

hey guys can you help me solve this problem from my kaplan workbook;
A hammer head with mass 500g is moving at 4m/s collides with a nail (m=4g) and comes to a stop in 0.002 seconds. What is the average force acts n the nail during the time?

a. 10^6 N
b. 10^3 N
c. 8N
d. 8 X 10^3 N

#### AmbitiousMD

##### New Member
10+ Year Member
This is what I did...

Vfinal= 0 m/s
V initial= 4 m/s
t= 0.002 seconds
Used the equation

v=vinitial+at

0=(4m/s)+a(0.002)

Ended w/ a=2000 m/s

Plugged that into fnet=ma

Fnet=(500)(2000)

And got 1000000 AKA 10^6

Now, I don't know if when plugging in the m in fnet=ma to add the extra 4 g of the nail.. I didn't obviously.

Tell me what you're getting.

#### cathyrn

##### Junior Member
10+ Year Member
5+ Year Member
I used impulse and momentum...don't know if that was right unfortunately
F X CHANGE in time = mv

so F= .5kg x 4/.002 = 10^3
what is the answer that is given?

#### AmbitiousMD

##### New Member
10+ Year Member
^ Oh yes.. I forgot.. must convert grams to kilograms.

#### ssiding

##### Full Member
10+ Year Member
I don't know the answer. My tutor gave me a set of problems? I will not get the answers from him for another week.