Mechanics

Question 1

How is momentum conserved when ball is dropped from rest above ground?

Answer 1

⇝ In Newton’s 3rd Law: every action, has equal and opposite reaction

⇝ force on gravity acting on ball, also acts on Earth

⇝ Hence both gain same momentum as ball drops

Question 2

Equation of stopping distance

Answer 2

Sum of thinking distance and breaking distance

Question 3

Why is there greater force; if a material that does not deform; ( e.g. car hits a concrete wall )

Answer 3

There is no energy transferred to the material so elastic collision

change in momentum = 2* initial momentum

thus greater force

Question 4

Define Newton’s third law and state when it is considered?

Answer 4

⇝ when two objects are interacting, they exert equal and opposite forces each other

⇝ they must be separate objects

⇝ same type of force (e.g. weight)

Question 5

What is meant by the centre of mass of an object?

Answer 5

A resultant force applied will not cause the object to rotate

Question 6

Which point in a projectile has the highest speed

Answer 6

towards the end/ before hitting the ground

Question 7

Is the vertical speed towards the end of projectile greater or smaller than initial vertical speed

Answer 7

greater

Question 8

one way in which the pairs of forces in 3rd law is same

Answer 8

same magnitude
forces are the same kind
same line of action

Question 9

one way in which pairs of forces are different

Answer 9

different bodies
forces in opposite direction

Question 10

n revolutions per second means

Answer 10

frequency

Question 11

how to draw kinetic energy graph from oscillation

things to remember

Answer 11

kinetic energy can’t be negative

energy zero at intervals

Question 12

what is the equation of torque

Answer 12

force x distance between 2 forces