If the bone does not move, then we know that the resultant acceleration on it is zero. That means that the net force must also equal zero. 

In other words, the sum of the two forces acting on the bone must be zero.

$\displaystyle F_{net}=F_1+F_2$

$\displaystyle 0N=F_1+F_2$

Since the forces are pulling in opposite directions, one force must be in the negative direction.

$\displaystyle 0N=F_1+(-F_2)$

From here, it's simple manipulation to see that the forces are equal.

$\displaystyle F_2=F_1$

The forces are equal in size, but going in opposite directions.

If no forces are acting upon the skater and he is on a frictionless surface, then that means he has no net acceleration.

Mathematically, we can see this relationship from Newton's second law:

$\displaystyle F=ma$

$\displaystyle 0N=ma$

$\displaystyle a=0\frac{m}{s^2}$

Presumably the skier has mass, therefore the acceleration must be zero.

If an object moves with a velocity and there is no acceleration, then the velocity remains constant. His velocity after five second will be equal to his initial velocity.

There is insufficient information to solve. Force is the product of mass and acceleration. While we are given the mass, we are not given an acceleration.

$\displaystyle F=ma$

If we assume that we are looking for the minimum force required to move the cabinet, then the force would be equal to the force of friction.

$\displaystyle F=-F_f$

Substitute the equations for frictional force and Newton's second law.

$\displaystyle ma=-(\mu F_N)$

Normal force is equal to the force of gravity.

$\displaystyle ma=-\mu (mg)$

The masses cancel out and we know the acceleration due to gravity is constant.

$\displaystyle a=-\mu (g)$

This equation is unsolvable as we do not know $\displaystyle \mu$, the coefficient of friction between the cabinet and the floor. We cannot find the acceleration of the cabinet, meaning we cannot find the force.

Acceleration results from a change in velocity. Despite the speed remaining constant, velocity is a vector quantity and will change if the car changes direction. In rounding the turn, there is a change in the direction of the velocity, but not in the magnitude. This change in direction causes a non-zero acceleration.

The acceleration will remain equal to the equation for centripetal acceleration:

$\displaystyle a_c=\frac{v^2}{r}$

As long as the magnitude of the velocity and the radius of the turn do not change, the acceleration will remain constant.

Force is given by the product of mass and acceleration. If an object has a constant velocity, then it has no acceleration.

$\displaystyle a=\frac{v_2-v_1}{t}$

$\displaystyle v_2=v_1\rightarrow a=\frac{0}{t}=0\frac{m}{s^2}$

If an object has no acceleration, then it must also have no net force.

$\displaystyle F=ma$

$\displaystyle F=m*0\frac{m}{s}$

$\displaystyle F=0N$

No additional information is needed to solve this question.

Since the object is moving with a constant velocity, it has no acceleration. Acceleration is only produced by a change in the velocity.

$\displaystyle a=\frac{\Delta v}{\Delta t}$

$\displaystyle \Delta v=0\frac{m}{s}\rightarrow a=\frac{0\frac{m}{s}}{\Delta t}=0\frac{m}{s^2}$

If acceleration is zero, no force is produced. This conclusion comes from Newton's second law:

$\displaystyle F=ma$

Since the acceleration is zero:

$\displaystyle F=m*0\frac{m}{s^2}$

$\displaystyle F=0N$

Newton's second law states that:

$\displaystyle F=ma$

We are told that the force on the object remains constant, even after it breaks in half. The mass of the broken piece will be equal to half the mass of the total object.

$\displaystyle F_1=F_2$

$\displaystyle m_1=2m_2$

Using these values, we can set up equations for the initial and final accelerations.

$\displaystyle a_1=\frac{F_1}{m_1}$

$\displaystyle a_2=\frac{F_2}{m_2}=\frac{F_1}{\frac{1}{2}m_1}$

$\displaystyle a_2=2\frac{F_1}{m_1}=2a_1$

$\displaystyle a_2:a_1=2:1$

If the force remains constant while the mass is cut in half, the acceleration of the object will double. The ratio of the new acceleration to the old acceleration will be 2:1. If the question asked for the ratio of the old acceleration to the new one, it would be 1:2.

Newton's second law states that:

$\displaystyle F=ma$

We are given the mass of the object and the acceleration. Using these values, we can solve for the necessary force.

$\displaystyle F=5kg*3\frac{m}{s^{2}}$
$\displaystyle F=15N$

If an object is moving with constant velocity, then its acceleration must be zero.

$\displaystyle a=\frac{v_2-v_1}{t}$

$\displaystyle v_2=v_1\rightarrow a=\frac{v-v}{t}=\frac{0}{t}=0$

We can then look at Newton's second law. If the acceleration is zero, then the net force must also be zero.

$\displaystyle F=ma$

$\displaystyle F=m(0)=0N$

This means that the gravitational force and normal force cancel out, and the propulsion force of the car cancels out the force of friction. Forces may still be acting in respective directions, but the net sum of these forces is zero.

First we need to find the net force, which will be equal to the sum of the forces on the bone.

$\displaystyle F_{net}=F_1+F_2$

Since the forces are going in opposite directions, we know that one force will be negative (since force is a vector). Conventionally, right is assigned a positive directional value. The force to the left will be negative.

$\displaystyle F_{net}=22N+(-17N)$

$\displaystyle F_{net}=5N$

From here we can use Newton's second law to expand the force and solve for the acceleration, using the mass of the bone.

$\displaystyle F=ma$

$\displaystyle 5N=(0.07kg)a$

$\displaystyle \frac{5N}{0.07kg}=a$

$\displaystyle 71.4\frac{m}{s^2}=a$