P2 - Forces

Question 1

What is a vector quantity ?

Answer 1

One with a magnitude and a direction - such as force, velocity, displacement, acceleration, momentum etc.

Question 2

What is a scalar quantity ?

Answer 2

One with only a magnitude and no direction - such as speed, distance, mass, temperature, time etc.

Question 3

How are vector quantities represented in diagrams ?

Answer 3

As arrows with length showing the magnitude and the direction of the arrow showing the direction of the quantity.

Question 4

What is a contact force ?

Answer 4

One that requires the two objects to be touching for a force to act - such as friction, air resistance, tension in ropes etc.

Question 5

What is a noncontact force ?

Answer 5

When the objects don’t need to be touching for the force to act - such as magnetic forces, gravitational forces, electrostatic forces etc.

Question 6

What two categories do all forces fall under ?

Answer 6

Push or pull.

Question 7

What is an interaction pair ?

Answer 7

A pair of forces that are equal and opposite and act on two interacting objects.

Question 8

What are the effects of gravity ?

Answer 8

Anything near a large mass is attracted to it strongly - on the surface of a planet it makes things fall to the ground, and it gives everything weight.

Question 9

What is the difference between weight and mass ?

Answer 9

Mass is the amount of stuff in an object (with the same value anywhere in the universe for a given object), whereas weight is the force acting on an object due to gravity.

Question 10

How can an object have the same mass but multiple weights ?

Answer 10

Mass doesn’t change but because weight depends on gravitational field strength it can vary.

Question 11

How is weight measured ?

Answer 11

A force measured in newtons using a calibrated spring balance or newtonmeter.

Question 12

How is mass measured ?

Answer 12

Not a force, measured in kilograms using a mass balance.

Question 13

How can you calculate weight ?

Answer 13

Weight(N) = mass(kg) × gravitational field strength (N/kg)

Question 14

What is the gravitational field strength of earth and the moon ?

Answer 14

Roughly 9.81 N/kg on earth and 1.6 N/kg on the moon

Question 15

What is the relationship between mass and weight ?

Answer 15

They are directly proportional, what you do to one you do to the other. Can be written as W ∝ m

Question 16

What is ∝ ?

Answer 16

The direct proportionality symbol.

Question 17

What are free body diagrams ?

Answer 17

Diagrams that show all the forces acting on an object, along with their magnitude and direction.

Question 18

What is a resultant force ?

Answer 18

The overall force on a point or object.

Question 19

How can you find the resultant force of of forces along the same line ?

Answer 19

You add the ones in the same direction and subtracting any going in the opposite direction.

Question 20

What is work done ?

Answer 20

When a force moves an object through a distance, energy is transferred work is one on the object.

Question 21

How can you find how much work has been done ?

Answer 21

Work done(J) = force(N) × distance(m) // W = F × s

Question 22

How many newton meters are required to do 1 joule of work ?

Answer 22

1 J = 1 Nm

Question 23

How can you use scale drawings to find resultant forces acting in perpendicular directions ?

Answer 23

Draw all the forces acting on an object to scale tip to tail and find the hypotenuse of the triangle you’ve made and measure this length (the resultant force) and put back through your scale to find the force and measure the angle to find the bearing.

Question 24

P

Answer 24

91