Question

If a 20 N force acts on a 10 kg object for 0.5 seconds. If the object starts at rest, what would it’s new p (momentum) and v (velocity) be?

Answer 1

Answer:

$p=10\:\text{kgm/s}},\\v_f=1\:\text{m/s}$

Explanation:

From Newton's 2nd Law, we have $\Sigma F=ma$. We can use this to find the acceleration of object after 20 N (force) is applied to the 10 kg object.

Substituting given values, we have:

$\Sigma F=ma, \\20=10a,\\a=\frac{20}{10}=2\:\mathrm{m/s^2}$

Now that we have acceleration, we can find the final velocity of object (after 0.5 seconds) using the following kinematics equation:

$v_f=v_i+at$, where $v_f$ is final velocity, $v_i$ is initial velocity, $a$ is acceleration, and $t$ is time.

Solving for final velocity:

$v_f=0+2\cdot 0.5,\\v_f=\boxed{1\:\text{m/s}}$

The momentum of an object is given as $p=mv$. Since we've found the final velocity and mass stays constant, we have:

$p=10\cdot 1=\boxed{10\:\text{kgm/s}}$