Motion and Forces

Question 1

Define Acceleration

Answer 1

Rate of the change in velocity

Question 2

Equation for acceleration

Answer 2

Acceleration= change in velocity divided by the time taken

Question 3

Change in velocity is

Answer 3

Final velocity-initial velocity

Question 4

What is Newton’s first law?

Answer 4

When there is no resultant force an object that is stationary will remain stationary and an object in motion will continue in a straight line at constant speed.

Question 5

What is needed for acceleration?

Answer 5

Force/ a resultant force

Question 6

What does Newton’s Second Law say?

Answer 6

Resultant force = mass x acceleration
f=ma

Question 7

What two things make up stopping distance?

Answer 7

Thinking distance+ braking distance

Question 8

What factor affects both thinking and braking distance?

Answer 8

Speed

Question 9

Factors affecting thinking distance (generally about the person).

Answer 9

Alcohol. Tiredness. Age. Distractions.

Question 10

Factors affecting braking distance (about vehicle and road).

Answer 10

Road surface. Weight of car. Quality of brakes. Slope.

Question 11

Why does the box and parachute fall at a terminal/constant velocity?

Answer 11

Drag acts upwards, weight acts downwards. Drag and weight are balanced. Constant velocity means no acceleration (f=ma). When forces are balanced there is no acceleration.

Question 12

Why are arrows good for representing vector quantities?

Answer 12

Can show both size and direction. Can show where they act from/ their origin.

Question 13

Weight equals?

Answer 13

Mass x gravitational field strength

Question 14

Resultant force equals?

Answer 14

Mass x acceleration

Question 15

Step 1 of terminal velocity (skydiver has just jumped out of airplane)

Answer 15

Object accelerates due to resultant force downwards. Weight, acting downwards, is only force acting vertically at the moment.

Question 16

Step 2 of terminal velocity (skydiver is falling, still no parachute)

Answer 16

As object accelerates, speed and drag increase. Therefore, resultant force decreases and acceleration decreases .

Question 17

Step 3 of terminal velocity (skydiver reaches terminal velocity)

Answer 17

Eventually, drag equals weight. There is no resultant force and no acceleration. Object moves at constant speed- object has reached terminal velocity.

Question 18

Step 4 of terminal velocity (skydiver opens parachute)

Answer 18

Drag increases. Drag is greater than weight. Resultant force is upwards. Skydiver decelerates.

Question 19

Step 5 of terminal velocity (terminal velocity again)

Answer 19

Drag is reduced. Forces are balanced. Resultant force is zero. This terminal velocity is not as fast as previous terminal velocity.

Question 20

What is the difference between weight and mass?

Answer 20

Weight is the pull of a planet’s gravitational force acting on an object. Measured in Newtons. Weight can change depending on the planet’s gravitational field strength.
Mass is the amount of matter inside and object. Measured in kilograms. Mass stays the same.

Question 21

Light Gates

Answer 21

Object passes through gate and breaks a light beam. When beam of light is broken, timer is started. When beam is no longer broken, timer stops. Speed = length of object/ time beam broken.

Question 22

Stopwatch and ruler

Answer 22

Measure distance travelled (using ruler).
Timer how long it takes for object to travel distance (use stopwatch). Speed= distance/time

Question 23

Motion Sensor

Answer 23

Uses echolocation.
Sends out a sound pulse and starts a timer.
When sound pulse reflects off a surface and returns, the pulse is detected and the timer stops.
Distance= speed of sound x time taken to return.
Speed can then be calculated.

Question 24

What is Newton’s 1st Law?

Answer 24

Newton’s 1st Law says that the velocity of an object will only change if a resultant force is acting on the object. This applies to a stationary (still) or moving object. If an object is moving and there is no resultant force acting on it, the object will continue moving in the same direction at the same speed.
This means that the object will continue moving at the same velocity.
This also means that the velocity of an object will only change if a resultant force is acting on the object.

Question 25

Thinking distance

Answer 25

Distance travelled from when driver realises they need to brake to when they apply brakes.

Question 26

Braking distance

Answer 26

Distance car travels between the driver applying the brakes and the car stopping.

Question 27

Describe how you could measure the average speed of a cyclist going round a track.

Answer 27

1. Mark start and finish line.
2. Measure distance of one lap around the track using a trundle wheel.
3. Time how long it takes for cyclist to complete one lap of the track using a stopwatch.
4. Repeat and find an average.
5. Find speed using speed = distance over time.

Question 28

What happens to thinking distance when speed doubles?

Answer 28

Thinking distance also doubles.

Question 29

What happens to braking distance when speed doubles?

Answer 29

Braking distance quadruples.