#2 Forces and Pressure

Question 1

What is a force?

Answer 1

A push or pull that acts on an object

Question 2

What is the unit of force?

Answer 2

Newton (N)

Question 3

What are the 2 types of forces?

Answer 3

Contact force and action-at-a-distance forces

Question 4

What are the 3 contact forces?

Answer 4

friction (slows down sliding)
tension (pulling a rope)
elastic (goes back to original form after stretching)

Question 5

What are the 3 action-at-a-distance force?

Answer 5

gravitation (pen hits floor when you let go, no contact)
magnetic (attracts metal)
static electricity (lightning)

Question 6

What is the difference between mass and weight?

Answer 6

mass: amount of matter in an object
weight: force of gravity acting on an object

Question 7

What happens to your weight and mass when you’re on the moon?

Answer 7

Your mass stays the same but your weight is less because the force of gravity is different on earth than the moon

Question 8

What is a balanced force?

Answer 8

net force = 0

object is stationary

Question 9

What is unbalanced force?

Answer 9

net force = positive or negative (depends on situation)

object moves in the direction of the stronger force

Question 10

What is pressure?

Answer 10

The amount of force that acts on a given area of an object

Question 11

What are common units of pressure?

Answer 11

n/m² = 1 Pa (Pascal), KPa

Question 12

What is compression?

Answer 12

A decrease in volume of matter caused by force

Question 13

Are solids, liquids and gases easily compressed?

Answer 13

Solids and liquids normally do not compress because there is little room to push particles together.

Gases are easily compressible.

Question 14

What is the formula for pressure calculations?

Answer 14

pressure = force/area

Question 15

[Practice Question A] A football player is tackled by another player and lands with the combined weight of both players on his knee. If the combined weight of the players is 2400 N and the player’s knee measures 0.1 m by 0.1 m, how much pressure is exerted on the turf when the player lands on his knee?

Answer 15

p = f/a
p = 2400/0.1 × 0.1
p = 2400/0.01

p = 240 000 N/m²

Question 16

[Practice Question B] The tip of a hypodermic needle is pressed against someone’s skin with a force of 2 N. If the tip of the needle has an area of 0.000 001 m², what is the pressure exerted on the skin by the needle?

Answer 16

p = f/a
p = 2/0.000 001

p = 2 000 000 N/m²

Question 17

What happens if heated gas is trapped inside a container?

Answer 17

Gas particles bounce against the sides faster and more often. This means that the heated gas exerts more added pressure in the inside of the container. The added pressure can lead to an explosion.

Question 18

What happens to the particles of air inside a bottle as pressure is applied?

Answer 18

The particles will move closer together

Question 19

What will happen to the pressure if the force decreases?

Answer 19

The pressure will also decrease