Physics Exam Review

Flashcards based on physics questions about springs, energy, forces, and motion.

What additional measuring instrument is needed to investigate Hooke's Law with a spring?

A measuring instrument to measure the extension of the spring.

Explain how to investigate whether a spring obeys Hooke's Law.

Measure the original length of the spring. Add masses to the spring and measure the new length each time. Calculate the extension (new length - original length). Calculate the force applied by each mass (F=mg). Plot a graph of force against extension. If the graph is a straight line through the origin, then the spring obeys Hooke's Law.

What is the relationship between kinetic energy (KE), mass, and velocity?

KE = 1/2 * mass * velocity^2

What happens to the kinetic energy of the train when the driver applies the brakes?

It is transferred to thermal energy due to friction in the brakes and between the train and the rails. It can also be transferred to the surroundings as heat and sound.

Explain why passengers gain gravitational potential energy in a lift, even when they are below ground.

Gravitational potential energy is calculated relative to a reference point (zero level). Even when the lift is underground, passengers gain GPE as they move further away from the reference point (tunnel level).

Explain how sloping tunnels affect the amount of work done by brakes and the motor.

The upward slope converts some of the kinetic energy of the train into gravitational potential energy, reducing the amount of work the brakes need to do. The downward slope assists the motor as gravity helps to accelerate the train, reducing the amount of work the motor needs to do.

What is the downward force on the balloon immediately after the ropes are untied but before it moves?

9100 N

What is the relationship between unbalanced force, mass, and acceleration?

Unbalanced force = mass * acceleration

What is the initial acceleration of the balloon if the unbalanced force is 400 N and the mass is 910 kg?

0.44 m/s^2

Explain how the upward acceleration of the balloon changes during the first few seconds of flight.

As the balloon accelerates upwards, air resistance increases. This reduces the unbalanced force and therefore reduces the upward acceleration. Eventually, air resistance will equal the unbalanced force, and the balloon will reach a constant velocity.

Explain how pouring sand affects the upward acceleration of the balloon.

Pouring sand reduces the total mass of the balloon. This increases the unbalanced force (since upward force remains the same but weight decreases), leading to a greater upward acceleration.

What is the independent variable in the student’s prediction 'The greater the starting height, the greater the speed'?

The starting height of the toy car

What is the dependent variable in the student’s prediction 'The greater the starting height, the greater the speed'?

The speed of the toy car

State two factors that should be kept constant when testing the prediction.

The surface of the slope, the toy car used, and the angle of the slope.

What apparatus does the student need for the toy car investigation?

Ruler and stopwatch.

Describe what the student should do to test his prediction that the more weight the toy car has, the faster it will roll down the slope.

Measure the mass of each car / Add mass to the toy cars. Release each car from same starting position/height. Measure the time for each marked distance. Repeat and calculate average time. Use speed = distance/time to calculate speed