P5

Question 1

If a physical quantity has both magnitude and direction is it a vector or scalar quantity? Include an example

Answer 1

Vector. Example - Force, Velocity, Displacement, acceleration and momentum

Question 2

What equation links mass, gravitational field strength and weight? Include units

Answer 2

Weight (N) = Mass (kg) x Gravitational Field Strength (N/kg)

Question 3

Describe an investigation which would find the link between the force applied and the extension of a spring.

Answer 3

Measure the natural length of a spring (when no load is applied) with a ruler clamped to a stand. Add a mass to the spring and record the new length of the spring. Calculate the extension as the change in length (take away the natural length). Continue to add masses and calculate the extension.

Question 4

What is the typical speed of a person walking, running and cycling?

Answer 4

Walking - 1.5m/s
Running - 3m/s
Cycling - 6m/s

Question 5

What can be found by calculating the gradient of:

a) Distance - Time graphs
b) Velocity - Time graphs

Answer 5

a) Speed

b) Acceleration

Question 6

The terminal velocity of a skydiver is determined by which two forces acting on the person?

Answer 6

Weight and drag (caused by air resistance). If the two forces are equal then a sky diver has reached terminal velocity.

Question 7

What is Newton’s first law?

Answer 7

First - If the resultant force acting on an object is zero and the object is stationary, then the object will remain stationary. However if the object is moving, it will continue to move at the same speed and in the same direction. So velocity stays the same.

Question 8

What is Newton’s second law?

Answer 8

Second - The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to its mass. Force = mass x acceleration

Question 9

What is Newton’s third law?

Answer 9

Third - Whenever two objects interact, the forces they exert on each other are equal and opposite.

Question 10

What is the resultant force acting upon an object which moves with constant velocity (same speed and direction)?

Answer 10

The resultant force is zero according to Newton’s first law.

Question 11

Define stopping distance

Answer 11

Stopping distance = thinking distance + braking distance.
Thinking distance is how far the car travels during the driver’s reaction time.
Stopping distance is how far the car travels once brakes are applied.

Question 12

What effects the thinking distance of a vehicle?

Answer 12

This is reaction time so tiredness, drugs, speed and distractions.

Question 13

What effects the braking distance of the vehicle?

Answer 13

Adverse road conditions (wet or icy), poor brakes, poor tyre condition, speed.

Question 14

What is the difference between elastic and inelastic deformation of a spring?

Answer 14

An elastic object returns to it’s original shape and length after a force is removed, the extension is directly proportional to force applied.
Inelastic objects do not return to their original shape or length and the extension is not directly proportional to force applied.

Question 15

Why would we describe the orbit of a planet around a sun as acceleration?

Answer 15

The direction of the planet is constantly changing even though speed remains the same. Centripetal force due the sun’s gravity keeps the planet in orbit.

Question 16

Describe the shape of the line on a velocity-time graph for an object travelling at steady speed.

Answer 16

A straight, horizontal line.

Question 17

Air resistance is a form of drag, is it a frictional force. Describe how the design of a car can help to minimise air resistance. Describe why parachutes work in the opposite way.

Answer 17

The most important factor in reducing air resistance for a car is keeping the shape of it streamlined. this is where the object is designed to allow fluid (liquid or gas) to flow easily across it.
Parachutes work to maximise the amount of air resistance so that the person can slow down enough to hit the ground at a safe speed.

Question 18

Describe the term inertia

Answer 18

Inertia is the tendency of an object to continue in their State of rest or of uniform motion. It is used to describe Newton‘s first law of motion.

Question 19

What energy transfer occurs when a car brakes?
What effect does this have on the brakes?


Answer 19

Energy is transferred from kinetic energy stores of the wheels to the thermal energy stores of the brakes.
this causes the brakes to heat up. 

Question 20

Give two methods which can be used to measure someone’s reaction time. Recall typical reaction times.

Answer 20

use computer-based test (e.g. Clicking the mouse when the screen changes colour). Another Is the ruler drop test where, without giving any warnings, a ruler is dropped from zero between a person’s thumb and forefinger and they catch the ruler as quickly as possible. Both tests need to be repeated as it is hard to do the tests accurately. A typical reaction time is 0.2 to 0.9 seconds.