Forces Pt2

Question 1

Why will an object always slow down and stop

Answer 1

Friction (if on a solid)

Question 2

What increases as speed increases

Answer 2

The resistance in a gas or liquid such as air resistance, which works to slow an object down
Can be reduced by making an object more streamlined to allow gas or liquid around it

Question 3

What do objects falling through gases or liquids reach

Answer 3

Terminal velocity where the velocity reaches its maximum as acceleration gradually decreases

Question 4

What does terminal velocity depend on

Answer 4

Shape and area, a small area increases the terminal velocity and a parachute for example slows it down

Question 5

Newton’s first law

Answer 5

A resultant force is needed to make something start moving, speed up or slow down

Question 6

What happens if the resultant force is the same?

Answer 6

There is a constant velocity

Question 7

Resultant force equals

Answer 7

Mass times acceleration

Question 8

Newton’s second law

Answer 8

Force equals mass times acceleration

Question 9

Inertia

Answer 9

The tendency for an object to remain unchanged

An inertial mass is how difficult it is to change the velocity of an object

Question 10

Newton’s third law

Answer 10

When a force is applied, an equal and opposite force is returned
Things move because one is lighter

Question 11

Stopping distance

Answer 11

Thinking distance + braking distance

Question 12

Thinking distance is affected by

Answer 12

Your speed

Your reaction time

Question 13

Braking distance is affected by

Answer 13

Speed
Weather or road surface
Condition of tyres
Quality of brakes

Question 14

How do brakes work?

Answer 14

When the brake pedal is pushed, the brake pads are pressed on to the wheels which causes friction and work to be done and energy is transferred from the kinetic energy store in the wheels to the thermal energy store of the brakes
Faster means more Ke and more work done
Large braking force means large decelerations, breaks can overheat or you skid

Question 15

Typical reaction time and factors that affect it

Answer 15

0.2 to 0.9 seconds

Tiredness, drugs, alcohol, distractions

Question 16

Momentum equals

Answer 16

Mass times velocity

Question 17

Momentum before an event equals

Answer 17

Momentum after an event

Question 18

Conservation of momentum

Answer 18

Calculate momentum
Equals momentum after
Rearrange to find velocity or mass

Question 19

What causes a change in momentum

Answer 19

A force

The force changing it is equal to the rate of change of the momentum

Question 20

Non contact forces

Answer 20

Gravity, magnetism, electrostatic

Question 21

What to do if the force isn’t the same direction as the movement to find the work done?

Answer 21

Use trigonometry to find the force in the direction of the movement
Then multiply it by distance to find the work done

Question 22

What other value does the gain in kinetic energy equal?

Answer 22

The loss in gravitational potential energy
If you ignore air resistance
Gain in gravitational potential = loss in kinetic energy

Question 23

How to find the acceleration if it changes direction?

Answer 23

Make sure that the velocity to the left is a negative value

Question 24

Work using kinetic energy and gpe

Answer 24

Change in kinetic energy + change in gravitational potential energy

Question 25

Other power equation

Answer 25

P = F x s

Only if it is moving at a constant speed in the same direction as the power