# 2 Motion and Force Flashcards

In which part of the graph (A, B or C) is the object moving the fastest?

A

- gradient of the line is the steepest
- more distance covered per time
- faster speed

What is the difference between the force **upthrust** and **reaction force**?

**Up thrust** is created when an object displaces a fluid, such as a boat displacing water.

**Reaction force** is the upward force on a block which is resting on a solid surface.

What is the SI unit for force?

newton or N

What type of force is created between two magnets?

magnetic force

This force can be attractive or repulsive

In which graph/s is the object travelling at a constant speed?

a) and e)

gradient is constant throughout

If a person has a mass of 100 kg on Earth. What will their weight be?

*The gravitational field strength of the Earth is 10 N/kg*

W=mg

W = 100 kg x 10 N/kg

W = 1000 N

What feature of a velocity-time graph gives the acceleration?

gradient of velocity-time graph

Masses are attracted to each other. Planets are attracted to each other. Name the force acting between them.

Gravitational force

Describe what is happening in the graph and explain how you know.

The object is accelerating or speeding up from the starting position

The gradient of the line is increasing, therefore velocity is increasing.

Which sketch (red or green) represents a faster velocity?

Green- more steep line

Object is covering more distance per time

If an object has a 50 N force acting North and a 50N force acting south, what is the resultant force?

50 N - 50 N = 0 N

What is the SI unit for displacement or distance travelled?

metre or m

F= ma

Make acceleration the subject of the equation

a = F/m

Which of the following quantities are vectors?

mass

acceleration

force

speed

velocity

time

**acceleration**

**force**

**velocity**

In which part of the graph (A, B or C) is the object travelling back to the start.

C

-gradient of the line is negative

velocity is negative

-travelling in opposite direction to part A

What is the equation for average speed?

average speed = total distance travelled/ time taken

What type of force acts forward on a rocket?

Thrust

Thrust is created when an object throws something out in one direction- such as gases.

What type of force is reduced if an object is streamlined?

air resistance

Rockets can push gas out and downward and the rocket moves upward. What is the name of this upward force on the rocket?

Thrust

What feature of a velocity-time graph gives the acceleration?

gradient of velocity-time graph

What feature of a velocity-time graph gives the distance travelled?

area under a velocity-time graph

In which graph/s is the object decelerating?

d)

gradient is getting less steep

What can forces do to an object?

- change the speed of the object
*(accelerate or decelerate)* - change the direction of the object
- change the shape of the object

A horizontal line on a velocity-time graph shows?

constant velocity, no acceleration

A horizontal line on a distance-time graph shows what?

That the object is not moving, has zero speed

If a book is a rest on a table, what two forces are acting on it.

downward gravitational pull (or weight)

upward reaction force from table

If an object accelerates at 10 m/s2. How fast would it be travelling after 10 s if it started at rest?

It will gain 10 metres per second every second.

After 10 s if should be travelling at 100 m/s!

What feature of a distance-time graph gives the velocity?

gradient of distance-time graph

Which ticker tape shows an object which is decelerating?

ticker tape Z

- dots get closer together
- object is covering less distance per unit time
- object is slowing down

What can be done to reduce friction when an object is sliding on a surface?

- use oil or grease on the surfaces
- make the surfaces smoother
- blow air between the surfaces

In which part of the graph (A, B or C) is the object stopped?

B

Gradient is zero therfore speed is zero- obejct is not moving