Force and Momentum

Question 1

force definition

Answer 1

• anything which makes an object move or change velocity
• symbol = F
• units = N

Question 2

force equation

Answer 2

• F = m x a

- F is proportional to m x a

Question 3

momentum definition

Answer 3

• of a body is the product of its mass and velocity
• symbol = p
• unit = kgm/s

Question 4

momentum equation

Answer 4

p = m x v

Question 5

Newton’s first law of motion

Answer 5

all bodies will remain at rest/ at a constant velocity unless an external force acts on them

Question 6

Newton’s second law of motion

Answer 6

the rate of change of a body’s momentum is proportional to the net force applied and will act in the direction of the force

Question 7

Newton’s third law of motion

Answer 7

every action has an equal and opposite reaction

Question 8

proportionality

Answer 8

f  = m 
a = 1/m

Question 9

principle of conservation of momentum

Answer 9

the total momentum of a system before an interaction is equal to the total momentum of the system after the interaction, so long as no external force acts on it.

Question 10

conservation of momentum equation

Answer 10

(m1)(u1) + (m2)(u2) = (m1)(v1) + (m2)(v2)

Question 11

Newton’s Law of universal gravitation

Answer 11

every mass in the universe attracts every other mass, along the line of their centres, with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them

Question 12

universal gravitation equation

Answer 12

F = g(m1)(m2)/d²

Question 13

notes about gravitational force

Answer 13

• always attractive
• distance = distance between CENTRES
• size of g force is equal for both masses
• the point between two bodies at which a body is weightless is where the masses’ attractive forces cancel

Question 14

who discovered the universal gravitational constant G

Answer 14

Henry Cavendish

Question 15

Inverse square law of universal gravitation

Answer 15

• double distance = quarter force
• half distance = F x 4
• triple the distance = 1/9 force

Question 16

terminal velocity

Answer 16

• the maximum free-fall velocity an object can fall at due to air resistance
• retarding force of air resistance (drag) balances the downward force of gravity

Question 17

Force in lifts

Answer 17

- when lift is stopped; 
normal weight (50kg x 9.8)
- when lift ACCELERATES down at 2m/s²; 
lighter (50kg x (9.8 - 2)
- when lift ACCELERATES up at 3m/s²; 
heavier weight (50 kg x (9.8 + 3 )
- when lift is moving at a constant velocity!!
normal weight (50kg x 9.8)

Question 18

Friction

Answer 18

• a force that opposes motion (prevents one surface sliding over another)