Physics: Standard Level
Space, time and motion — Theme A
- 1.
A 2.0 kg block starts from rest on a horizontal frictionless surface. A constant resultant force of 3.0 N acts on it for 4.0 s. Determine the acceleration, the final speed and the displacement of the block.
[5 marks] - 2.
Marking analysis: A learner attempts the following task: “A 2.0 kg block starts from rest on a horizontal frictionless surface. A constant resultant force of 3.0 N acts on it for 4.0 s. Determine the acceleration, the final speed and the displacement of the block.” Their response addresses only this point: “Uses a = F/m = 3.0/2.0.” Evaluate the response against the complete 5-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[5 marks] - 3.
A ball is thrown horizontally at 15 m/s from the top of a 20 m cliff. Calculate the time to reach the ground and the horizontal distance travelled. Use g = 9.8 m/s².
[4 marks] - 4.
Marking analysis: A learner attempts the following task: “A ball is thrown horizontally at 15 m/s from the top of a 20 m cliff. Calculate the time to reach the ground and the horizontal distance travelled. Use g = 9.8 m/s².” Their response addresses only this point: “States that vertical and horizontal motion are independent, and uses the vertical equation 20 = ½(9.8)t² to find time.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 5.
Define linear momentum, and state the principle of conservation of momentum.
[2 marks] · no calculator - 6.
Marking analysis: A learner attempts the following task: “Define linear momentum, and state the principle of conservation of momentum.” Their response addresses only this point: “Defines momentum as the product of an object's mass and velocity (p = mv), a vector quantity.” Evaluate the response against the complete 2-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[2 marks] · no calculator - 7.
A 0.50 kg ball moving at 8.0 m/s collides head-on with a stationary 1.5 kg ball, and they stick together. Calculate their common velocity after the collision.
[3 marks] - 8.
Marking analysis: A learner attempts the following task: “A 0.50 kg ball moving at 8.0 m/s collides head-on with a stationary 1.5 kg ball, and they stick together. Calculate their common velocity after the collision.” Their response addresses only this point: “Uses conservation of momentum: total momentum before = total momentum after.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 9.
State the work-energy theorem, and use it to explain why a car's braking distance depends on the square of its initial speed.
[3 marks] · no calculator - 10.
Marking analysis: A learner attempts the following task: “State the work-energy theorem, and use it to explain why a car's braking distance depends on the square of its initial speed.” Their response addresses only this point: “States that the work done by the resultant force on an object equals its change in kinetic energy.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 11.
A crane lifts a 500 kg load through a vertical height of 12 m in 20 s at constant speed. Calculate the useful power output of the crane. Use g = 9.8 m/s².
[4 marks] - 12.
Marking analysis: A learner attempts the following task: “A crane lifts a 500 kg load through a vertical height of 12 m in 20 s at constant speed. Calculate the useful power output of the crane. Use g = 9.8 m/s².” Their response addresses only this point: “Calculates the weight lifted: 500 × 9.8 = 4900 N.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 13.
A car of mass 1200 kg travelling at 20 m/s brakes and comes to rest over a distance of 40 m. Calculate the average braking force, using the work-energy theorem.
[4 marks] - 14.
Marking analysis: A learner attempts the following task: “A car of mass 1200 kg travelling at 20 m/s brakes and comes to rest over a distance of 40 m. Calculate the average braking force, using the work-energy theorem.” Their response addresses only this point: “Calculates the initial kinetic energy: ½ × 1200 × 20² = 240 000 J.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 15.
An object moves in a horizontal circle of radius 0.50 m at a constant speed of 4.0 m/s. Calculate its centripetal acceleration and state the direction of the resultant force causing it.
[3 marks] - 16.
Marking analysis: A learner attempts the following task: “An object moves in a horizontal circle of radius 0.50 m at a constant speed of 4.0 m/s. Calculate its centripetal acceleration and state the direction of the resultant force causing it.” Their response addresses only this point: “Uses centripetal acceleration a = v²/r.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] - 17.
State Newton's third law of motion, and use it to explain the forces acting when a swimmer pushes against the water to move forward.
[3 marks] · no calculator - 18.
Marking analysis: A learner attempts the following task: “State Newton's third law of motion, and use it to explain the forces acting when a swimmer pushes against the water to move forward.” Their response addresses only this point: “States Newton's third law: for every action force, there is an equal and opposite reaction force acting on a different object.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks] · no calculator - 19.
A ball of mass 0.20 kg is dropped from rest and hits the ground 1.5 s later. Calculate its momentum just before impact, and the impulse delivered to it by gravity during the fall. Use g = 9.8 m/s².
[4 marks] - 20.
Marking analysis: A learner attempts the following task: “A ball of mass 0.20 kg is dropped from rest and hits the ground 1.5 s later. Calculate its momentum just before impact, and the impulse delivered to it by gravity during the fall. Use g = 9.8 m/s².” Their response addresses only this point: “Uses v = gt = 9.8 × 1.5 to find the speed just before impact.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 21.
A 1.0 kg trolley moving at 6.0 m/s collides elastically with a stationary 1.0 kg trolley. Determine the velocities of both trolleys after the collision, and verify that both momentum and kinetic energy are conserved.
[4 marks] - 22.
Marking analysis: A learner attempts the following task: “A 1.0 kg trolley moving at 6.0 m/s collides elastically with a stationary 1.0 kg trolley. Determine the velocities of both trolleys after the collision, and verify that both momentum and kinetic energy are conserved.” Their response addresses only this point: “States that momentum conservation requires m₁u₁ = m₁v₁ + m₂v₂.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 23.
A ball is kicked with an initial speed of 20 m/s at an angle of 30° above the horizontal. Calculate the time taken to reach maximum height, and the total time of flight, assuming it lands at the same height from which it was kicked. Use g = 9.8 m/s².
[5 marks] - 24.
Marking analysis: A learner attempts the following task: “A ball is kicked with an initial speed of 20 m/s at an angle of 30° above the horizontal. Calculate the time taken to reach maximum height, and the total time of flight, assuming it lands at the same height from which it was kicked. Use g = 9.8 m/s².” Their response addresses only this point: “Resolves the initial vertical velocity component: uᵧ = 20 sin30° = 10.0 m/s.” Evaluate the response against the complete 5-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[5 marks] - 25.
A spring with spring constant 200 N/m is stretched by 0.15 m within its elastic limit. State Hooke's law, and calculate the elastic potential energy stored in the spring.
[4 marks] - 26.
Marking analysis: A learner attempts the following task: “A spring with spring constant 200 N/m is stretched by 0.15 m within its elastic limit. State Hooke's law, and calculate the elastic potential energy stored in the spring.” Their response addresses only this point: “States Hooke's law: F = kx, valid within the elastic limit of the spring.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 27.
A 5.0 kg block rests on a frictionless slope inclined at 30° to the horizontal. Calculate the component of the block's weight acting parallel to the slope, and hence its acceleration down the slope. Use g = 9.8 m/s².
[4 marks] - 28.
Marking analysis: A learner attempts the following task: “A 5.0 kg block rests on a frictionless slope inclined at 30° to the horizontal. Calculate the component of the block's weight acting parallel to the slope, and hence its acceleration down the slope. Use g = 9.8 m/s².” Their response addresses only this point: “Calculates the weight of the block: 5.0 × 9.8 = 49 N.” Evaluate the response against the complete 4-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[4 marks] - 29.
An electric motor is supplied with 400 J of electrical energy and does 260 J of useful work lifting a load against gravity. Calculate the efficiency of the motor, and state one reason why the efficiency is less than 100%.
[3 marks] - 30.
Marking analysis: A learner attempts the following task: “An electric motor is supplied with 400 J of electrical energy and does 260 J of useful work lifting a load against gravity. Calculate the efficiency of the motor, and state one reason why the efficiency is less than 100%.” Their response addresses only this point: “Uses efficiency = (useful energy output ÷ total energy input) × 100%.” Evaluate the response against the complete 3-mark task. Identify what earns credit and state every additional requirement needed for full marks.
[3 marks]