Section 1- Forces and Motion P2

Question 1

What is Newton’s third law of motion?

Answer 1

If object A exerts a force on object B then object B exerts an equal and opposite force on object A.
-if you push against something like a shopping trolley then it will push back against you just as hard

Question 2

What is the equation linking mass, velocity and momentum?

Answer 2

Momentum(kg m/s) = Mass(kg) x Velocity(m/s)

Question 3

What is the rule about momentum before and after a collision?

Answer 3

Momentum before = Momentum after

Momentum is conserved when no external forces act.

Question 4

What is the equation linking change in momentum, time and force?

Answer 4

change in momentum(kg m/s)
Force(N) = ——————————————-
time(s)

Question 5

What are the safety precautions in a car?

Answer 5

CRUMPLE ZONES- increase the time taken for the car to stop
SEAT BELTS- stretch slightly, increasing the time taken
AIR BAGS- slow you down more gradually

Question 6

What is the equation linking force, moment and perpendicular distance?

Answer 6

moment(Nm) = force(N) x perpendicular distance(m)

Question 7

Describe a practical for how you can find the centre of gravity of a flat object:

Answer 7

• suspend a shape and a plumb line from the same point and wait until they stop moving
• draw a line on the shape
• do the same again but suspend the shape from a different pivot point
• the centre of gravity is where the two lines cross

Question 8

Where is the centre of gravity?

Answer 8

The centre of gravity hangs directly below the point of suspension

Question 9

What is the principle of moments?

Answer 9

If an object is balanced then the:

total anticlockwise moment = total clockwise moment

Question 10

What happens if the moments aren’t equal?

Answer 10

If the total anticlockwise moments do not equal the total clockwise moments, there will be a resultant moment