Explain the difference between a scalar and a vector quantity.
Sort these into scalars and vectors: mass, velocity, force, temperature, displacement, speed, acceleration, energy, momentum.
Resolve each force into horizontal and vertical components.
Two forces act at a point: 3.0 N east and 4.0 N north. Find the magnitude and direction of the resultant.
A velocity has components 6.0 m s−1 east and 8.0 m s−1 north. Find the resultant speed and its direction.
Two forces act at a point: 10 N due east and 10 N at 60 degrees north of east. Using components, find the magnitude and direction of the resultant.
A block of weight 50 N rests on a slope at 30 degrees to the horizontal. Find the component of the weight along the slope and the component perpendicular to the slope.
Two forces of equal size F act at a point. Explain why the resultant can be anything from 0 to 2F, and state the angle between the forces in each of these two cases.
Total: 27 marks. Original work by the TheLucidSTEM team. Written in the style of the papers; no past paper question is reproduced.
Answer key · full worked solutionsclick to reveal
a scalar has magnitude only; a vector has both magnitude and direction.
scalars: mass, temperature, speed, energy. Vectors: velocity, force, displacement, acceleration, momentum.
B1. Fx = 20 cos 30° = 17.3 N; Fy = 20 sin 30° = 10.0 N.
B2. Fx = 50 cos 60° = 25.0 N; Fy = 50 sin 60° = 43.3 N.
B3. Fx = 8.0 cos 45° = 5.7 N; Fy = 8.0 sin 45° = 5.7 N.
R = √(3.02 + 4.02) = 5.0 N; tan θ = 4.0 / 3.0, so θ = 53° north of east.
R = √(6.02 + 8.02) = 10.0 m s−1; tan θ = 8.0 / 6.0, so θ = 53° north of east.
total x = 10 + 10 cos 60° = 10 + 5 = 15 N. Total y = 0 + 10 sin 60° = 8.66 N.
R = √(152 + 8.662) = √(225 + 75) = √300 = 17.3 N. Direction: tan θ = 8.66 / 15, so θ = 30° north of east.
component along the slope = 50 sin 30° = 25 N; component perpendicular to the slope = 50 cos 30° = 43.3 N.
the resultant is largest, 2F, when the forces point the same way (angle 0 degrees), and smallest, 0, when they point in opposite directions (angle 180 degrees). For angles between these the resultant lies between 0 and 2F.