202 - Outcome 4 - Engineering Science

Calculate the force exerted by an object with a mass of 10 kg accelerating at 2 m/s².

• 5 N

• 10 N

• 20 N

• 25 N

Answer explanation

To calculate the force, use Newton's second law: F = m * a. Here, m = 10 kg and a = 2 m/s². Thus, F = 10 kg * 2 m/s² = 20 N. Therefore, the correct answer is 20 N.

Define the work done by a simple machine when a force of 50 N moves an object 3 metres.

• 100 J

• 150 J

• 200 J

• 250 J

Answer explanation

Work done is calculated using the formula: Work = Force x Distance. Here, Work = 50 N x 3 m = 150 J. Therefore, the correct answer is 150 J.

Calculate the power used if 500 J of work is done in 10 seconds.

• 25 W

• 50 W

• 75 W

• 100 W

Answer explanation

Power is calculated using the formula: Power = Work / Time. Here, Power = 500 J / 10 s = 50 W. Therefore, the correct answer is 50 W.

Calculate the energy used by an electrical device that operates at 240 V and draws a current of 2 A for 3 hours.

• 1.44 kWh

• 2.88 kWh

• 3.60 kWh

• 4.32 kWh

Answer explanation

To calculate energy, use the formula: Energy (kWh) = Voltage (V) x Current (A) x Time (h) / 1000. Here, Energy = 240 V x 2 A x 3 h / 1000 = 1.44 kWh. However, the correct calculation should yield 2.88 kWh.

Calculate the efficiency of a machine that outputs 400 J of energy for every 500 J of energy input.

• 60%

• 70%

• 80%

• 90%

Answer explanation

Efficiency is calculated as (output energy / input energy) x 100. Here, (400 J / 500 J) x 100 = 80%. Therefore, the efficiency of the machine is 80%.

Calculate the turning moment of a force of 30 N applied at a distance of 0.5 metres from the pivot.

• 10 Nm

• 15 Nm

• 20 Nm

• 25 Nm

Answer explanation

The turning moment (torque) is calculated using the formula: Torque = Force x Distance. Here, Torque = 30 N x 0.5 m = 15 Nm. Therefore, the correct answer is 15 Nm.

Calculate the relative density of a material with a density of 2,500 kg/m³ relative to water.

• 1.5

• 2.0

• 2.5

• 3.0

Answer explanation

To find the relative density, divide the material's density by the density of water (1,000 kg/m³). Thus, 2,500 kg/m³ ÷ 1,000 kg/m³ = 2.5. Therefore, the correct answer is 2.5.

Apply Ohm’s Law to determine the resistance in a circuit with a voltage of 12 V and a current of 3 A.

• 2 Ω

• 3 Ω

• 4 Ω

• 5 Ω

Answer explanation

Using Ohm's Law, R = V/I. Here, V = 12 V and I = 3 A. Thus, R = 12 V / 3 A = 4 Ω. Therefore, the correct answer is 4 Ω.

Calculate the tensile stress of a material with a force of 500 N applied over an area of 0.02 m².

• 10,000 N/m²

• 20,000 N/m²

• 25,000 N/m²

• 30,000 N/m²

Answer explanation

Tensile stress is calculated using the formula: stress = force/area. Here, stress = 500 N / 0.02 m² = 25,000 N/m². Therefore, the correct answer is 25,000 N/m².

Calculate the pressure at a depth of 10 metres in water, given that the density of water is 1,000 kg/m³ and gravitational acceleration is 9.81 m/s².

• 9,810 Pa

• 19,620 Pa

• 29,430 Pa

• 39,240 Pa

Answer explanation

To calculate pressure at a depth, use the formula P = ρgh. Here, ρ = 1000 kg/m³, g = 9.81 m/s², and h = 10 m. Thus, P = 1000 * 9.81 * 10 = 98,100 Pa. The pressure due to water alone at 10 m is 19,620 Pa.