# Forces using Newtons Second law

• gotpink74
In summary, the conversation discusses the deceleration of a bullet fired into wet clay and how to calculate the average force it exerts on the block of clay. The hint suggests using one of the kinematic equations and then applying Newton's second law to determine the net force. It is possible for the acceleration and force to be negative in certain situations.

## Homework Statement

A bullet fired into wet clay will decelerate fairly uniformly. If a 10 g bullet hits a block of clay at 235 m/s and comes to rest in 17 cm, what average force does it exert on the block? [Hint: From the fact that the bullet goes from vi to 0 in a distance s, you can find aav and with that Fav.]

ƩF=mg

## The Attempt at a Solution

These are all of the answers I have gotten wrong
46.94 N

13.82 N

23.5 N

The hint is telling you to use one of the kinematic equations to solve for the acceleration of the bullet. Once you solve for it, then use Newton 2 in the horizontal direction to solve for the net force acting on it in the horizontal direction.

how do you find the acceleration of the bullet

gotpink74 said:
how do you find the acceleration of the bullet

Look up and memorize the kinematic equations for constant accelertion. pick the one that works best for the given problem. The bullet travels a given distance in the block with a given initial speed. It's final speed is 0 after it travels the given distance in the block.

is it possible for the acceleration to be negative

gotpink74 said:
is it possible for the acceleration to be negative
Why sure. Like when you hit the brakes, the car is moving forward in a positive direction, but the acceleration is in the negative direction, with the braking force acting in the negative direction to slow the car down. If you then hit the gas pedal, the car speeds up again and the acceleration is positive.

can the force be negative i got -1624.26

gotpink74 said:
can the force be negative i got -1624.26
Yes, you are quite right , but don't forget the units and round off the answer to say F = -1600 N.