P10- Force and motion

Question 1

How to investigate the effect of acceleration on an object of constant mass?

Answer 1

-Set up a level track with a trolley attached to string off edge of table
-Attach full weight stack to end of the string (force)
-Switch on datalogger, enter card length and release glider
-Record acceleration, do 3 times, calculate mean
-Repeat experiment with dif masses on end of string, placing mass on car instead
-Mass of car and hanger is constant

Question 2

Newton’s second law of motion

Answer 2

Acceleration of an object is…
-Proportional to the resultant force acting on the object
-Inversely proportional to mass of the object

Question 3

Inertia

Answer 3

The tendency of an object to stay at rest or in uniform motion

Question 4

Inertial mass

Answer 4

Ratio of force over acceleration
How difficult it is to change the velocity of an object

Question 5

When does the velocity of an object increase?
When does the velocity of an object decrease?

Answer 5

If resultant force is in the same direction of velocity
If resultant force is in opposite direction of velocity

Question 6

Resultant force if an object falls with no other forces acting on it?

Answer 6

Weight

Question 7

Weight

Answer 7

Force acting on an object due to gravity

Question 8

Mass

Answer 8

Quantity of matter in an object

Question 9

Terminal velocity

Answer 9

The velocity an object will eventually reach when falling, resultant force is zero.

Question 10

Gravitational field strength and unit

Answer 10

Gravitational force on a 1kg object N/kg

Question 11

Resultant force if an object falls in a fluid?

Answer 11

-Fluid drags on the object due to friction
-Resultant force is its weight minus the drag force

Question 12

Acceleration if an object falls in a fluid

Answer 12

Decreases as it falls, frictional force increases

Question 13

Velocity if an object falls in a fluid

Answer 13

-Reaches constant velocity when frictional force= weight
-Resultant force is 0
-Called terminal velocity

Question 14

2 things braking force depends on

Answer 14

Speed of vehicle-Increases KE of car
Mass of vehicle-Increases KE of car

Question 15

Stopping distance is what?

Answer 15

Thinking distance and braking distance

Question 16

Thinking distance

Answer 16

Distance travelled by a vehicle in the time it takes for a driver to react

Question 17

Why does the driver’s reaction time affect the thinking distance?

Answer 17

Distance = speed x time so the longer the reaction time, the longer the distance

Question 18

Braking distance

Answer 18

Distance travelled by a vehicle during the time the braking force acts

Question 19

Factors that affect thinking distance and what effect they have?

Answer 19

Tiredness, alcohol, drugs, distractions
Increase thinking distance

Question 20

Factors that affect braking distance and what effect they have?

Answer 20

Speed of car, adverse road conditions, condition of brakes and tyres
Increases braking distance

Question 21

Law of conservation of momentum

Answer 21

In a closed system, the total momentum before an event is equal to the total momentum after an event

Question 22

Conservation of momentum equation when two objects travel apart

Answer 22

(mass of A x velocity of A) = -(mass of B x velocity of B)

Question 23

Conservation of momentum when two objects travel apart explained

Answer 23

Minus sign shows momentum of B is in opp direction to A
Both have equal and opp amounts of momentum
Total momentum after=total momentum before

Question 24

Impact time affecting impact force?

Answer 24

The greater the impact time, the more the impact force is reduced

Question 25

Force equation using time, mass, velocity

Answer 25

Force= mass x change in velocity / time

Question 26

When two vehicles collide what 2 things are the same?

Answer 26

The force exerted on each other Their total momentum

Question 27

Cycle helmets and cushioned surfaces affecting impact?

Answer 27

Reduce impact forces by increasing impact time

Question 28

Seat belts and air bags affecting impact?

Answer 28

Reduce impact forces by increasing impact time and spreading force across the chest

Question 29

Crumple zones affecting impact?

Answer 29

Give way on impact so increases impact time, reduces impact force

Question 30

Elastic meaning

Answer 30

When an object returns to original shape when forces are removed

Question 31

Hooke's Law practical

Answer 31

Attach spring and ruler to clamp stand Use G-clamp to secure clamp stand Measure original length of spring with ruler Add one mass to spring, record its length, measure from same point Calculate extension (new length-original) Repeat until all masses added to spring Plot graph

Question 32

Axis for Hooke's law practical? Gradient for stiff spring? Medium stiff? Soft spring?

Answer 32

X axis- extension Y axis- force Steep gradient Less steep gradient Shallow gradient

Question 33

Hooke's law

Answer 33

Force applied to a spring and its extension are directly proportional, as long as its limit of proportionality isn't exceeded

Question 34

What happens to the force and extension relationship when it is beyond the limit of proportionality?

Answer 34

Extension of spring is no longer proportional to applied force

Question 35

What is meant by 'centre of mass'?

Answer 35

The point where the mass appears to be concentrated