Question

hockey is a sport in which players use hockey sticks to push a puck across smooth ice. at practice one day, three different - colored hockey pucks were sliding on the ice. the green hockey puck has less mass than the black and purple hockey pucks, which have the same mass. a player hit each hockey puck with a stick, but not from the same direction. use the information in the diagram to answer. which puck(s) experienced the strongest force when hit? how do you know? before green puck: 100 g (less mass) speed: 14 m/s black puck: 170 g (more mass) speed: 20 m/s purple puck: 170 g (more mass) speed: 17 m/s after speed: 24 m/s (speeded up by 10 m/s) speed: 30 m/s (speeded up by 10 m/s) speed: 7 m/s (slowed down by 10 m/s) all three hockey pucks experienced the same force because they changed speed by the same amount. the black hockey puck; it is more massive and has the fastest ending speed the purple hockey puck; it takes a stronger force to slow down a more massive object than to speed it up. the black and purple hockey pucks; they have more mass than the green puck, but changed speed by the same amount.

Explanation:

Step1: Recall Newton's second law

Force $F = ma$, where $m$ is mass and $a$ is acceleration. Acceleration $a=\frac{\Delta v}{\Delta t}$. Assuming the time - interval $\Delta t$ is the same for all pucks, we can compare forces based on mass and change in velocity $\Delta v$.

Step2: Calculate change in velocity for each puck

For the green puck: Initial speed $v_1 = 14$ m/s, final speed $v_2=24$ m/s, $\Delta v_{green}=24 - 14=10$ m/s.
For the black puck: Initial speed $v_1 = 20$ m/s, final speed $v_2 = 30$ m/s, $\Delta v_{black}=30 - 20 = 10$ m/s.
For the purple puck: Initial speed $v_1 = 17$ m/s, final speed $v_2 = 7$ m/s, $\Delta v_{purple}=|7 - 17| = 10$ m/s. The magnitudes of the changes in velocity are the same for all pucks.

Step3: Compare masses

The green puck has mass $m_{green}=100$ g. The black and purple pucks have mass $m_{black}=m_{purple}=120$ g. The black and purple pucks have more mass than the green puck.

Step4: Determine the force

Since $F = ma$ and $\Delta v$ (and thus $a$ assuming same $\Delta t$) is the same for all pucks, and the black and purple pucks have more mass, they experience a greater force.

Answer:

The black and purple hockey pucks; they have more mass than the green puck, but changed speed by the same amount.