Movement Y10

Question 1

What is speed?

Answer 1

Distance ÷ time

Question 2

What is the difference between speed and velocity?

Answer 2

Velocity has a direction, speed does not

Question 3

What is acceleration?

Answer 3

How fast an object changes its velocity
Acceleration = (velocity final - velocity initial) ÷ time
Measured in m/s^2

Question 4

What is force?

Answer 4

Force = mass x acceleration

Question 5

How does force relate to acceleration?

Answer 5

Force is proportional to acceleration

Question 6

What is the acceleration of a rocket of mass 50kg and thrust 1200N?

Answer 6

Weight = 50 x 10 = 500N
Overall force = 1200-500 = 700N
Acceleration = 700 ÷ 50 = 14m/s^2

Question 7

What is terminal velocity?

Answer 7

When acceleration and overall force are both 0

Question 8

What are the three stages of an object falling?

Answer 8

1) object accelerates downwards due to weight. No drag ∴ overall force downwards
2) as object gains speed, air resistance increases, but weight stays same, so overall force decreases. Acceleration also decreases
3) eventually drag balanced weight, so no overall force or acceleration. Now it has reached terminal velocity.

Question 9

How can you increase terminal velocity?

Answer 9

Increase the force to increase the acceleration

Make it more streamlined to decease the air resistance

Question 10

What is thinking time and what can affect it?

Answer 10

Time to react to what you see. Tiredness, visibility, drug/alcohol use, concentration

Question 11

What is stopping time and what can affect it?

Answer 11

Time between putting foot in break and stopping. Tyres, conditions, breaks, ground

Question 12

In a distance time graph, what does the gradient represent?

Answer 12

Speed

Question 13

In a velocity time graph, how do you find the distance?

Answer 13

Area enclosed

Question 14

How do you work out a moment?

Answer 14

Moment(Nm/Ncm) = force x distance

Question 15

If a person moves from left to right on a bridge, what will happen and why?

Answer 15

The CM will increase, therefore Rr must increase. To do this, Rr’s force must increase.

Question 16

What is Hooke’s law?

Answer 16

Force is proportional to extension, as long as elastic limit has not been reached

Question 17

What are elastic and plastic behaviour?

Answer 17

Elastic = when force removed spring goes back to original length
Plastic = when force removed spring stays a bit stretched

Question 18

What does a spring’s graph tell you?

Answer 18

Straight line through origin ∴ force proportional to extension
F = K x E

Question 19

What is the spring constant in 2x springs?

Answer 19

In series: 0.5K

In parallel: 2K

Question 20

What is a force? (newton’s 1st law)

Answer 20

That which causes an object to accelerate

Question 21

What is Newton’s third law?

Answer 21

• for every action there is an equal but opposite reaction
∴ for a force to exist there must be two objects. The size of the force on each object will be the same, but they don’t cancel out, as act on different objects
E.g. When you jump up the earth has a downward gravitational pull on you of 500N, but you have an upward gravitational pull on the earth of 500N

Question 22

What is momentum? Is it vector/scalar?

Answer 22

• momentum = mass x velocity
• measured in kgm/s
• vector ∴ direction imp
• you may need to say the direction of the momentum

Question 23

What is the principle of conservation of momentum?

Answer 23

Total momentum before an action=total momentum after reaction as long as no external forces, e.g. Friction etc.

Question 24

Wat do you do in explosion problems?

Answer 24

• total m to left = total m to right

* ∴ work out m on one side, then that will be m on other. Therefore you can solve for 1 unknown

Question 25

What do you do in collision problems?

Answer 25

Subtract the momentum of one object from the momentum of the other object to find the overall m. (remember direction v important)
Then using the PoCoM:
Total mass x velocity = the m you worked out before
Solve for whatever you need to know

Question 26

What is newton’s 2nd law?

Answer 26

Force = change in m /time

Question 27

How does newton’s 2nd law have an effect on car safety/crashes/jumping?

Answer 27

In these cases you want smallest possible force, to avoid injury ∴ as we can’t change the initial/final momentum, what we, use do is increase the time taken
We do this by bending knees on impact/crumple zones in cars/airbags

Question 28

How can changing forces affect speed and direction?

Answer 28

• upwards and downwards forces are balanced
• accelerating: forwards force greater than backwards force
• decelerating: backwards force (drag/friction) greater than forwards force
• direction will travel in whatever direction the force is greatest

Question 29

How do car safety devices work in relation to momentum?

Answer 29

They try to increase time take for car’s/person’s momentum to reach 0 ∴ less force on person
• crumple zones crush during a collision ∴ increase time take for m to reach 0
• airbags also increase time for person’s momentum to reach 0
• seat belts stop you tumbling around inside and are slightly stretchy ∴ reduce time for m to reach 0