Topic 1.2: Forces and Momentum Questions

A 0.45 kg ball travelling at 14 m s⁻¹ is caught by a fielder and brought to rest in 0.060 s.

Determine the magnitude of the average force the fielder's hands exert on the ball.

A solid brass cylinder of volume 4.0 × 10⁻⁴ m³ is fully submerged in water of density 1.0 × 10³ kg m⁻³ (g = 9.8 N kg⁻¹).

Calculate the buoyancy force on the cylinder.

State the condition that must be met for the total momentum of a system of objects to be conserved during a collision.

A 0.45 kg ball experiences a single net force of 6.0 N.

Calculate the magnitude of its acceleration.

State Newton's first law of motion.

A cork floats at rest, partly submerged, on the surface of still water.

Identify the two forces acting on the cork and state the relationship between their magnitudes.

State what is meant by the static friction force acting on an object.

A 2.5 kg block sliding on a frictionless surface speeds up from 3.0 m s⁻¹ to 11 m s⁻¹ along a straight line.

Calculate the impulse delivered to the block.

State what is meant by the terminal velocity of an object falling through a fluid.

A satellite moves in a circular orbit around a planet at a constant speed.

State the direction of the net force acting on the satellite, and state why the satellite is accelerating even though its speed does not change.

A single force of 200 N acts on a trolley at 52° above the horizontal.

Calculate the horizontal and vertical components of this force.

(cos 52° = 0.62, sin 52° = 0.79)

State what is meant by the momentum of an object, and explain why momentum is a vector quantity.

State Archimedes' principle.

State what is meant by an object being in translational equilibrium.

A box rests on a rough ramp tilted at 25° to the horizontal and stays still.

(a) State the three forces acting on the box and draw a labelled free-body diagram in words.

(b) The box has weight 60 N. Resolve the weight into components parallel and perpendicular to the ramp surface. (sin 25° = 0.42, cos 25° = 0.91)

In an experiment a student measures the friction force on a sliding block as 6.0 N when the normal force is 24 N.

(a) Determine the coefficient of dynamic friction.

(b) Outline why this coefficient has no unit.

(c) State what happens to the friction force if the normal force is doubled (μ_d unchanged).

Two boxes sit on a smooth floor: a 5.0 kg box behind a 3.0 kg box, joined by a light string.

A horizontal force of 24 N pulls the 3.0 kg front box.

Calculate the acceleration of the pair and the tension in the connecting string.

A 0.40 kg ball moving at 6.0 m s⁻¹ collides head-on and sticks to a stationary ball of mass 1.2 kg (three times its mass).

Calculate the percentage of the original kinetic energy that is lost in the collision.

Two solid spheres, P and Q, are tied to the bottom of a tank and held completely submerged in the same oil. Sphere P has radius 2.0 cm and sphere Q has radius 6.0 cm. The oil is uniform and both spheres are fully covered by it.

What is the ratio (buoyancy force on Q) : (buoyancy force on P)?

A 3.0 kg block is driven up a smooth vertical wall by a constant force of 45 N pushing straight up.

Taking g = 9.8 m s⁻², determine the block's acceleration up the wall.