A jet ski is a small boat built for carrying one or two people and moving at high speed on water. Fig. 1.1 shows a student riding on a jet ski. Inside the jet ski, a pump forces a high-speed jet of water backwards out of the rear. Fig. 1.1 includes labels for the arrow showing the direction of movement, the jet ski, and the jet of water.
(a(i))[1]
Fill in the word equation to show how the resultant force on an object is linked to the change in momentum of the object.
resultant force =
(a(ii))[2]
Over 2.0 s, the pump increases the backward speed of 180 kg of water by 30 m/s. Calculate the backward force exerted on the water.
(b(i))[2]
Using Newton’s third law of motion, explain why the jet ski experiences a forwards force.
(b(ii))[2]
The student has a mass of 70 kg and the jet ski has a mass of 280 kg. Use your answer from (a)(ii) to work out the acceleration of the student and jet ski when no resistive forces act.
(c)[3]
At a speed of 20 m/s, calculate the total kinetic energy of the student and jet ski.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Resultant force = the rate at which momentum increases (or increase in momentum per unit time)” …