Paper 1 Forces Drills

Q1

Which statement about a free-body diagram is correct?

A. It should include the resultant force as an extra arrow.
B. It should show only forces acting on the chosen body.
C. It should show all forces exerted by the chosen body.
D. It should omit weight if the body is supported.

Q2

A block rests on a horizontal table. Which force is the Newton’s third-law partner of the normal force exerted by the table on the block?

A. weight of the block
B. gravitational force exerted by the block on Earth
C. force exerted by the block on the table
D. friction exerted by the table on the block

Q3

The weight of a $2.50\mathrm{kg}$ mass is approximately

A. $0.255\mathrm{N}$
B. $2.50\mathrm{N}$
C. $24.5\mathrm{N}$
D. $245\mathrm{N}$

Q4

A force of magnitude $40\mathrm{N}$ acts at $30^{\circ }$ above the horizontal. Its horizontal component is

A. $20\mathrm{N}$
B. $34.6\mathrm{N}$
C. $46.2\mathrm{N}$
D. $80\mathrm{N}$

Q5

For an object in translational equilibrium,

A. the resultant force is zero.
B. the resultant moment is necessarily non-zero.
C. the object must be at rest.
D. no forces act on it.

Q6

A force of $12\mathrm{N}$ acts perpendicular to a spanner at a distance $0.25\mathrm{m}$ from the pivot. The moment is

A. $0.021\mathrm{N}\mathrm{m}$
B. $3.0\mathrm{N}\mathrm{m}$
C. $12.25\mathrm{N}\mathrm{m}$
D. $48\mathrm{N}\mathrm{m}$

Q7

The unit of pressure is equivalent to

A. $\mathrm{N}\mathrm{m}$
B. $\mathrm{N}{\mathrm{m}}^{-1}$
C. $\mathrm{N}{\mathrm{m}}^{-2}$
D. $\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$

Q8

A spring obeys Hooke’s law. Doubling the extension

A. halves the force.
B. doubles the force.
C. leaves the force unchanged.
D. quadruples the force.

Q9

The gradient of a force-extension graph for a spring within the limit of proportionality gives

A. spring energy.
B. force constant.
C. extension.
D. pressure.

Q10

Upthrust on an immersed object is equal to

A. the object’s weight always.
B. the weight of fluid displaced.
C. the object’s mass.
D. the pressure at the top of the object.

Q11

For a falling object reaching terminal velocity,

A. weight becomes smaller.
B. drag becomes larger until it equals weight.
C. acceleration increases to $g$.
D. resultant force becomes downward and constant.

Q12

Which quantity is a vector?

A. pressure
B. force
C. density
D. mass

Q13

A couple consists of

A. two equal parallel forces in the same direction.
B. two unequal forces meeting at one point.
C. two equal and opposite parallel forces separated by a distance.
D. a single force acting through a pivot.

Q14

The centre of gravity of a body is

A. always at the geometric centre.
B. the point through which the resultant weight may be considered to act.
C. the point where normal contact force must act.
D. always inside the material of the body.

Q15

A body is more stable when

A. its centre of gravity is higher and base is narrower.
B. its centre of gravity is lower and base is wider.
C. its weight is zero.
D. its normal force is smaller than its weight.

Q16

Hydrostatic pressure at depth $h$ in a liquid of density $\rho$ is

A. $\rho gh$
B. $\rho g/h$
C. $h/(\rho g)$
D. $\rho h/g$

Q17

A normal contact force is always

A. vertical.
B. equal to weight.
C. perpendicular to the contact surface.
D. opposite to velocity.

Q18

Friction on a stationary object on a rough surface

A. must be zero.
B. must have its maximum possible value.
C. acts to oppose the tendency of relative motion at the contact.
D. always acts opposite to the object’s weight.

Q19

A force has no moment about a pivot when

A. its line of action passes through the pivot.
B. it is horizontal.
C. it is vertical.
D. it is smaller than the weight.

Q20

Which statement about force components is correct?

A. Components are extra forces added to the original force.
B. Components replace the original force in a chosen coordinate description.
C. Components can only be used for horizontal forces.
D. Components must always have equal magnitudes.