Anouk rolls a loaded warehouse cart across a flat floor at 2 m/s. Then she rolls the same cart empty, again at 2 m/s. She stops each cart with her hands.
Which cart takes more stopping?
The two runs match in every way but one: the speed is 2 m/s both times, and only the mass differs.
Loaded, the cart's mass is about 60 kg. Empty, it is about 12 kg.
Stopping a cart means bringing its velocity to zero.
To stop the loaded cart in the same time, Anouk must exert a larger force on it.
In earlier grades you saw why: the same force gives a smaller acceleration to a larger mass.
With a smaller acceleration, the loaded cart loses its velocity more slowly. So with the same force, it takes longer to stop.
Either way Anouk tries it, a larger force for the same time or the same force for a longer time, the loaded cart is harder to stop.
Two sleds slide across a frozen pond at the same speed. One carries a load of firewood; the other is empty. Which sled is harder to stop?
A bowling ball and a soccer ball roll across a gym floor at the same speed. Which ball is harder to stop?
A loaded wheelbarrow and an empty wheelbarrow are rolled across a yard at the same speed. Which is harder to stop?
The speeds are equal, so only the masses differ.
The loaded wheelbarrow has more mass.
The loaded wheelbarrow is harder to stop.
Two identical gym balls roll across a floor at the same speed. Which ball is harder to stop?
The speeds are equal, and the masses are equal too.
Nothing differs between the two balls.
Neither: the two balls are equally hard to stop.
Dmitri says: 'Two canoes drift toward a dock at the same speed. The canoe carrying camping gear takes more stopping, because it has more mass.' Is Dmitri correct?
Three identical wagons roll along a sidewalk at the same 1.5 m/s. The first carries bricks, 80 kg in total. The second carries mulch, 30 kg in total. The third is empty, 10 kg in total. Which wagon is hardest to stop?
Celia must stop two rolling luggage carts, one loaded and one empty, both moving at the same speed. Which feature decides which cart is harder to stop?
A loaded concrete truck and a skateboarder coast along a flat street at the same slow speed. Which statement is correct?