Question

A filled shopping cart $\left(30.0kg\right)$ is being pushed rapidly toward the back of a store so that its velocity is $-2.0m/s$. What is the momentum of the cart, and what is the kinetic energy of the cart?

• A. Momentum $60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $60.0J$
• B. Momentum $-60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $60.0J$
• C. Momentum $60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $-60.0J$
• D. Momentum $-60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $-60.0J$
• E. Momentum $60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $120.0J$

Answer 1

The correct option is B Momentum $-60.0\left(kg\right)\left(m\right)/s$, Kinetic energy $60.0J$

Given : $v=-2.0$ $m/s$ $m=30.0$ kg

Momentum of the cart $P=mv=30.0\times (-2.0)=-60.0$ $kg.m/s$

Kinetic energy of the cart $K.E=\frac{1}{2}m{v}^2=\frac{1}{2}\times 30.0\times (-2.0{)}^2=60.0$ J