MEDIUM
AS and A Level
IMPORTANT
Earn 100

The wind is blowing a boat with force F. The motor of the boat can exert a driving force of D N, where D<F. Show with a diagram that, whatever direction the wind is taking the boat with the motor switched off, the motor is capable of deflecting the direction by a maximum of sin-1DF.

Important Questions on Forces in Two Dimensions

HARD
AS and A Level
IMPORTANT
A building is unstable after a natural disaster. A car is stuck under the building and needs to be dragged out as quickly as possible, although the exact direction is less important. Three people can pull ropes, one due north, one at a bearing of 010° and one at a bearing of 030°. Akhil can pull with a force of 300 N, Ben can pull with a force of 240 N and Khadijah can pull with a force of 210 N. Find who should pull each rope to maximise the acceleration and what the net force will be.
MEDIUM
AS and A Level
IMPORTANT

Three forces act on a particle in equilibrium in the horizontal plane, as shown in the diagram. Find the size of the unknown force F and the angle θ.

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HARD
AS and A Level
IMPORTANT

Three forces act on a particle in equilibrium in the horizontal plane, as shown in the diagram. By resolving in a direction perpendicular to F, show that θ=47.2° and find F.

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HARD
AS and A Level
IMPORTANT
Two people drag a car of mass 1200 kg forward with ropes. One pulls with force 400 N on a bearing of 005°. One pulls with force 360 N on a bearing of 352°. Find magnitude of the acceleration and its direction to the nearest 0.1°.
HARD
AS and A Level
IMPORTANT

A boat is in equilibrium held by a rope to the shore. The rope exerts a force T at an angle θ from north. The wind blows the boat with force 40 N in a northwest direction. The current pushes it south with a force of 50 N. Show that Tsinθ=202 and find an expression for Tcosθ. Hence, show that tanθ=8+10217 and find θ and T.

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HARD
AS and A Level
IMPORTANT
A car of mass 300 kg is on a slope, which is at an angle of 5° to the horizontal. When it is pulled down the slope by a rope parallel to the slope with a force of T, it accelerates at 2 m s-2. Find the acceleration of the car when it is pulled up the slope by a rope parallel to the slope with a force of T..
HARD
AS and A Level
IMPORTANT
A girl can drag a stone block of mass 18 kg up a slope at an angle of 13° to the horizontal with an acceleration of 0.7 m s-2. Assuming this is the maximum force she can exert to drag the block, find the mass of the heaviest stone block she would be able to drag up the slope.
HARD
AS and A Level
IMPORTANT
A ball of mass m kg slides down a slope, which is at an angle of θ° to the horizontal. It passes two light gates x m apart. At the first gate, the speed of the ball is measured as u m s-1, and at the second its speed is measured as v m s-1. Assuming the resistance is constant, show the resistance force has a total size of m2x2xgsinθ+u2-v2.