This diagram is from a rowing club investigation of a boat moving through water. Fig. 1 shows two horizontal forces on the boat at one instant. The forward ...
Question 1 Report
This diagram is from a rowing club investigation of a boat moving through water. Fig. 1 shows two horizontal forces on the boat at one instant. The forward force from the oars is 820 N and the water resistance is 610 N. The combined mass of the boat and crew is 350 kg.
(a) Complete the equation for resultant force.
resultant force = forward force − ................. [1]
(b) Calculate the acceleration of the boat at this instant. [3]
(c) State what happens to the boat's velocity if the forward force and water resistance become equal. [1]
(d) Explain why water resistance increases when the speed of the boat increases. [2]
Answer Details
(a) \[\text{resultant force}=\text{forward force}-\text{water resistance}\] Water resistance may also be called drag. [1]
(b) \[F_{\text{resultant}}=820\text{ N}-610\text{ N}=210\text{ N}\] \[F=ma\] \[a=\frac{210\text{ N}}{350\text{ kg}}=0.60\text{ m/s}^2\] [3]
(c) If the forward force equals water resistance, the resultant force is zero. The boat continues at constant velocity, meaning constant speed in a straight line. [1]
(d) At higher speed, more water must be pushed aside each second. This produces a greater drag, or water-resistance force. [2]
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