Motion and Forces

Question 1

Explain the term scalar quantity and give examples

Answer 1

A quantity with just a magnitude
Examples: speed, distance, mass, energy, time

Question 2

Explain the term vector quantity and give examples

Answer 2

A quantity with magnitude and a direction.
Examples: velocity, displacement, force, momentum, acceleration

Question 3

What is velocity?

Answer 3

Speed with a stated direction.

Question 4

What are some important factors to distance/time graphs? (5)

Answer 4

1. Gradient is velocity
2. Sharper gradient means faster speed.
3. Horizontal lines means stationary.
4. Area under line = nothing.
5. Curved line means that the velocity is changing.

Question 5

What are some important factors to velocity/time graphs? (5)

Answer 5

1. Gradient is acceleration.
2. Sharper gradient means acceleration.
3. Horizontal lines constant speed.
4. Area under line = distance travelled
5. Curved line means that the acceleration is changing

Question 6

How to use light gates to determine the speed? (4)

Answer 6

1. Set up two light gates, one at the start and one at the end.
2. Measure distance between them.
3. As soon as the object passes through the first gate, it will measure the time taken to reach the second light gate.
4. Then use speed=distance/time. This method is more accurate as it removes reaction time and human error with a stopwatch.

Question 7

Recall typical speeds:
wind
sound
walking
running
cycling
bus
train
plane

Answer 7

wind: 5-7ms^-1
sound: 340ms^-1
walking: 5km/h = ~1.4ms^-1
running: ~6 miles per hour = ~3ms^-1
cycling: 15km/hh = ~4ms^-1
bus: 14km/h
train: 125miles/h
plane: 900km/h

Question 8

What is newtons first law?

Answer 8

An object has a constant velocity unless acted on by a resultant force.

Question 9

Recall newtons first law and what happens when the resultant force is zero (2)

Answer 9

1. No acceleration
2. So moving at a constant velocity or the object is at rest.

Question 10

Recall newtons first law and what happens when the resultant force is not zero (2)

Answer 10

1. Acceleration is change in velocity over time.
2. So the velocity will change and the direction or speed of the object will change (or both).

Question 11

What is inertial mass?

Answer 11

This is a measure of how difficult it is to change the velocity of an object.
Inertial mass = force/acceleration

Question 12

What is Newtons Third Law?

Answer 12

Every action force has an equal and opposite reaction force.

Question 13

What is momentum?

Answer 13

Momentum is always conserved in a collision (where there are no external forces like friction, air resistance, electrostatic attraction).

Question 14

What is the Ruler Drop Experiment? (4)

Answer 14

1. Someone else holds a ruler just above your open hand.
2. They drop it at a random time.
3. Record the distance from the bottom of the ruler to the point where it was caught.
4. Average these values.

Question 15

What is the stopping distance made up of?

Answer 15

thinking distance and braking distance

Question 16

Factors that affect thinking distance (5)

Answer 16

1. speed
2. concentration
3. tiredness
4. distractions
5. influence of drugs/alcohol

Question 17

Factors that affect braking distance (4)

Answer 17

1. speed
2. poor road conditions (icy, wet)
3. bald tires (low friction)
4. mass (more passengers)

Question 18

What are the dangers of large decelerations? (3)

Answer 18

1. When there is a crash, there is a large deceleration over a very short time as you stop moving from a high speed.
2. As force = mass x acceleration , this large deceleration means a great force is exerted on the car and the passengers.
3. This force can cause an injury.