Chapter 11: Forces

Question 1

What is the difference between vector and scalar quantities?

Answer 1

Vector quantities need direction for them to be valid, whereas scalar are just numbers.

Question 2

Name some everyday forces

Answer 2

Weight, friction, air resistance, drag, engine force, lift, upthrust

Question 3

What is the resultant force?

Answer 3

The single force that can replace a set of forces giving the same motion

Question 4

What type of force is friction?

Answer 4

Friction is a force that opposes motion.

Question 5

What equation links resultant force, mass and acceleration?

Answer 5

force = mass x acceleration

Question 6

What is the equation for weight?

Answer 6

weight = mass x gravity

Question 7

What is the unit for force?

Answer 7

Newtons

Question 8

What is the unit for acceleration?

Answer 8

ms^-2

Question 9

What is the unit for gravity?

Answer 9

N/kg

Question 10

What is the unit for mass?

Answer 10

kilograms

Question 11

What is the stopping distance?

Answer 11

thinking distance + braking distance

Question 12

What is the thinking distance?

Answer 12

The distance traveled in the time between seeing the car and putting your foot on the brake

Question 13

What is the braking distance?

Answer 13

The distance travelled in the time between your foot being on the brake and the car stopping.

Question 14

Give some examples of factors that can affect the thinking distance.

Answer 14

Being drunk, ill, or on drugs; fog or other weather making it harder to see

Question 15

Give some examples of factors that can affect the braking distance.

Answer 15

icy roads, worn tyres, worn brakes

Question 16

Explain the relationship between the two opposing forces during terminal velocity

Answer 16

At terminal velocity, the two opposing forces are balanced.

Question 17

Give some examples of vector quantities.

Answer 17

velocity, acceleration, displacement

Question 18

Give some examples of scalar quantities.

Answer 18

speed, distance

Question 19

What is the motion of an object with a resultant force of zero?

Answer 19

Newton’s First Law: Every object continues in a state of rest or of uniform motion unless there is a resultant force acting.

Question 20

What is the motion of an object with a positive resultant force?

Answer 20

The object has started moving or changing speed - it is going to the right

Question 21

What is the motion of an object with a negative resultant force?

Answer 21

The object has started moving or changing speed - it is going to the left

Question 22

Explain the motion of a parachutist in terms of resultant force, drag and weight

Answer 22

When the parachutist first jumps out of the plane, there is no upward force, and so there is a large resultant force downwards, so they accelerate quickly. The air resistance increases as the parachutist’s speed increases, and so they accelerate slowly. The air resistance and weight are balanced and so the parachutist travels at a constant high speed, and has reached terminal velocity. The parachutist opens their parachute, and the large air resistance causes them to decelerate quickly. The air resistance decreases as the parachutist’s speed decreases, and so they decelerate slowly. The air resistance and weight balance again, and so the parachutist reaches a new lower terminal velocity.

Question 23

How to investigate acceleration due to gravity in an experiment using a light gate?

Answer 23

Drop the picket fence (alternating opaque and transparent sheet) through the light gate; results will be recorded on the computer via the data logger

Question 24

What is Newton’s Second Law?

Answer 24

The effect of a resultant force depends on how big the force is, the direction in which it is acting and the mass of the object.

Question 25

How to investigate acceleration due to gravity in an experiment using ticker tape?

Answer 25

Attach ticker tape to a mass and drop the tape through the machine. Measure distance between two dots on the ticker tape for two spaces. Find the velocity for each pair, and from there, find the acceleration.