Podcast
Questions and Answers
What is the effect of doubling the speed of a car on the braking distance, assuming the braking force remains constant?
What is the effect of doubling the speed of a car on the braking distance, assuming the braking force remains constant?
- The braking distance remains the same.
- The braking distance doubles.
- The braking distance quadruples. (correct)
- The braking distance halves.
When calculating distance travelled during acceleration, which equation is likely used?
When calculating distance travelled during acceleration, which equation is likely used?
- Distance = Initial Velocity × Time + 0.5 × Acceleration × Time² (correct)
- Speed = Distance / Time
- Distance = Time × Acceleration
- Velocity = Distance / Time + Acceleration
If a car has an initial speed of 20 m/s and the braking force remains unchanged, what will happen to the kinetic energy when the speed is increased to 40 m/s?
If a car has an initial speed of 20 m/s and the braking force remains unchanged, what will happen to the kinetic energy when the speed is increased to 40 m/s?
- Kinetic energy decreases.
- Kinetic energy increases fourfold. (correct)
- Kinetic energy doubles.
- Kinetic energy remains constant.
What factors can influence the braking distance of a car, apart from speed?
What factors can influence the braking distance of a car, apart from speed?
What is the relationship between kinetic energy and braking distance?
What is the relationship between kinetic energy and braking distance?
Which of the following calculations is essential for determining the distance travelled while accelerating?
Which of the following calculations is essential for determining the distance travelled while accelerating?
During an emergency stop, which scenario would likely result in a shorter braking distance?
During an emergency stop, which scenario would likely result in a shorter braking distance?
If a car's speed is increased from 30 m/s to 60 m/s, how does the kinetic energy change?
If a car's speed is increased from 30 m/s to 60 m/s, how does the kinetic energy change?
Which statement best describes the motion of the car when horizontal forces are balanced?
Which statement best describes the motion of the car when horizontal forces are balanced?
What is the correct equation to calculate distance travelled using speed and time?
What is the correct equation to calculate distance travelled using speed and time?
How do you calculate the acceleration of the car if it speeds up from 9m/s to 18m/s in 6 seconds?
How do you calculate the acceleration of the car if it speeds up from 9m/s to 18m/s in 6 seconds?
Which equation correctly relates resultant force, mass, and acceleration?
Which equation correctly relates resultant force, mass, and acceleration?
If the mass of the car is 1120 kg and the driver's mass is 80 kg, what would their total mass be?
If the mass of the car is 1120 kg and the driver's mass is 80 kg, what would their total mass be?
What is the resultant force acting on the car if its total mass is 1200 kg and it accelerates at 3 m/s²?
What is the resultant force acting on the car if its total mass is 1200 kg and it accelerates at 3 m/s²?
What would happen if the resultant force acting on the car becomes zero?
What would happen if the resultant force acting on the car becomes zero?
Which of the following describes a scenario in which the car is speeding up?
Which of the following describes a scenario in which the car is speeding up?
What is the useful energy output from an electric motor used to lift a load?
What is the useful energy output from an electric motor used to lift a load?
What typically happens to the wasted energy in an electric motor?
What typically happens to the wasted energy in an electric motor?
Based on the graph, what can be concluded about the relationship between the load lifted and input energy needed?
Based on the graph, what can be concluded about the relationship between the load lifted and input energy needed?
Why are some escalators turned off when the shop is not busy?
Why are some escalators turned off when the shop is not busy?
If an escalator motor has a power of 4000 W and runs for 8 hours daily, how many kilowatt-hours does it consume in a week?
If an escalator motor has a power of 4000 W and runs for 8 hours daily, how many kilowatt-hours does it consume in a week?
How much does it cost to run one escalator for an average week?
How much does it cost to run one escalator for an average week?
What is the average power of one escalator motor mentioned in the content?
What is the average power of one escalator motor mentioned in the content?
What energy type is primarily not useful in the operation of an electric motor lifting a load?
What energy type is primarily not useful in the operation of an electric motor lifting a load?
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Study Notes
Motion of the Car
- Car can be stationary, have constant speed, speed up, or slow down based on forces acting on it.
- Constant speed implies no net acceleration resulting from balanced forces.
Distance, Speed, and Time
- Distance can be calculated using the equation: distance travelled = speed × time.
Acceleration Calculation
- Acceleration determined by formula:
- acceleration = (final speed - initial speed) / time
- For a car accelerating from 9 m/s to 18 m/s in 6 seconds:
- acceleration = (18 m/s - 9 m/s) / 6 s = 1.5 m/s²
Resultant Force and Acceleration
- The relationship between acceleration, mass, and resultant force is given by:
- resultant force = mass × acceleration.
Calculating Resultant Force
- Total mass of car and driver = 1120 kg + 80 kg = 1200 kg.
- Resultant force during acceleration calculated with the previously defined equation.
Distance During Acceleration
- Use kinematic equations to calculate distance while accelerating, formula typically involves initial speed, time, and acceleration.
Braking Distance and Kinetic Energy
- Braking distance increases quadratically with speed increase due to kinetic energy (KE = 1/2 mv²).
- Doubling speed quadruples kinetic energy, leading to longer stopping distance.
Electric Motor Energy Transfer
- Electric motor converts electrical energy into both useful and wasted energy.
- Useful energy output is often mechanical energy used to lift loads.
Wasted Energy
- Wasted energy often dissipates as heat, contributing to inefficiency in energy transfer.
Input Energy and Load Relationship
- Increased load lifted by a motor results in higher input energy requirements, showcasing a direct relationship.
Escalator Energy Efficiency
- Each escalator motor's power: 4000 W, operational for 8 hours/day, 6 days/week.
- Electricity cost calculated by converting power to kilowatts and multiplying by time and cost per kilowatt-hour.
- Costs to run one escalator can be determined via: cost = power (kW) × time (h) × price per kWh.
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