Question

calculating kinetic energy and work
a 600 kg car is at rest, and then accelerates to 5 m/s.
what is its original kinetic energy? □ j
what is its final kinetic energy? □ j
how much work was used? □ j

Explanation:

Step1: Recall Kinetic Energy Formula

The formula for kinetic energy (KE) is $KE = \frac{1}{2}mv^2$, where $m$ is mass and $v$ is velocity.

Step2: Calculate Original Kinetic Energy

The car is at rest initially, so $v = 0\ m/s$, $m = 600\ kg$.
Substitute into the formula: $KE_{original} = \frac{1}{2} \times 600\ kg \times (0\ m/s)^2 = 0\ J$.

Step3: Calculate Final Kinetic Energy

Final velocity $v = 5\ m/s$, $m = 600\ kg$.
Substitute into the formula: $KE_{final} = \frac{1}{2} \times 600\ kg \times (5\ m/s)^2 = \frac{1}{2} \times 600 \times 25 = 7500\ J$.

Step4: Calculate Work Done

By the work - energy theorem, work done (W) is equal to the change in kinetic energy.
$\Delta KE=KE_{final}-KE_{original}=7500\ J - 0\ J = 7500\ J$, so $W = 7500\ J$.

Answer:

Original kinetic energy: $\boldsymbol{0}$ J; Final kinetic energy: $\boldsymbol{7500}$ J; Work used: $\boldsymbol{7500}$ J