Chapter 3 Forces & Energy

Question 1

Which diffuses faster - large particles or small particles? Why?

Answer 1

Small particles, because they are lighter and move faster

Question 2

How can you increase the speed of an object?

Answer 2

Increase the force of the object in the direction of movement

Question 3

How do you find the average speed of a vehicle?

Answer 3

Total distance / Total time

Question 4

Compare the terms “accuracy” and “precision”

Answer 4

Accuracy is how close your measured value is to your known/true value, which precision is how close your measured values are to each other

Question 5

Define the term “moment of a force”. What is the moment of a force dependent on?

Answer 5

Moment of a force describes the turning effect of a force.
Moment is dependent on the size of the force and the distance between the pivot and the position where the force acts.

Question 6

How will putting more air in a ball change the pressure inside the ball?

Answer 6

The pressure increases because there are more particles in the ball.

Question 7

How does diffusion work?

Answer 7

Particles bumping into each other repeatedly until equally spaced out. The particles move from a region of higher concentration to a region of lower concentration

Question 8

How do you calculate the moment of a force?

Answer 8

Force x distance to the pivot

Question 9

How do you calculate pressure?

Answer 9

Force / Area

Question 10

Why is a thumbtack able to pierce through objects?

Answer 10

Because it has a small surface area on its tip

Question 11

Why do dams increase the thickness of the concrete the further down they go?

Answer 11

Because the pressure increase the further down you go below sea level

Question 12

How can camels hold up their weight on the soft and loose sand of the desert?

Answer 12

Camels have wide feet that increases surface area, so the pressure exerted on the sand is less and they are able to balance.

Question 13

How does a pressure cooker work?

Answer 13

Water and food are placed inside the cooker, which has a sealed lid. When the water boils, the steam cannot escape so the pressure and temperature of the gas inside increases. On top of the pressure cooker, there is a weight to control the pressure and valves that allow steam to escape once the require pressure has been reached.

Question 14

A bicycle is moving in a straight line. There is an unbalanced force opposite to the direction the bicycle is moving. Describes what happens.

Answer 14

The bicycle will slow down.

Question 15

What conditions will increase the speed of diffusion?

Answer 15

A bigger difference in concentration of particles, and a higher temperature.

Question 16

An Olympic sprinter completes the 100m race in a time of 10s. Calculate the average speed of the sprinter.

Answer 16

Speed = Distance / Time = 100/10 = 10m/s

Question 17

A hammer is used to push a nail into wood. The area of the nail is 1.5mm2. The pressure needed for the nail to go into the wood is 50N/mm2. Calculate the force needed from the hammer.

Answer 17

Pressure = Force/area
So,
Force = Pressure x Area
Force = 50 x 1.5 = 75N

Question 18

What are the 2 variables that affect atmospheric pressure?

Answer 18

• The concentration of gas particles
• The weight of air above a person’s current position
  (the higher you go in the atmosphere, the lower the concentration of gas particles, and the lower the weight of air)

Question 19

When you pump out all the air in a metal container, what will you see? Why?

Answer 19

The container is crushed. The pressure inside the container becomes close to zero but the pressure outside does not change, so the container is crushed by the atmospheric pressure

Question 20

What is a vacuum

Answer 20

A space without any particles