A sled and rider, gliding over horizontal, frictionless ice at 5.1m/s , have a combined mass of 74kg . The sled then slides over a rough spot in the ice, slowing down to 2.5m/s .
What impulse was delivered to the sled by the friction force from the rough spot?
The magnitude of the impulse is equal to the decrease of the momentum.
Impulse = 74 * (5.1 – 2.5) = 192.4
The impulse is -192.4 kg * m/s.