P2.2

Question 1

State one way in which the force of gravity is different to the electrostatic force.

Answer 1

• The force of gravity is only attractive.
• The electrostatic force can be either attractive or repulsive, depending upon whether there are unlike or like charges interacting respectively.

Question 2

What is a field

Answer 2

the region where electrical/magnetic/mass bodies experience a force.

Question 3

Newtons 3rd law

Answer 3

When two bodies interact, they exert a force upon each other that is equal in size, but opposite in direction

Question 4

Explain why the force of water resistance is greater than the force of air resistance

Answer 4

As water is more dense than air, it contains more particles (mass) than air, thus more particles collide and interact, exerting a greater force of resistance.

Question 5

How to calculate resultant force if they act 90° to each other

Answer 5

• draw a force triangle
• join two forces head to tail
• resultant force is the hypotenuse

Question 6

How to resolve a force

Answer 6

Make a triangle out of the force

• the force itself is the hypotenuse
• its components are the sides
• use trig identities

Question 7

Resolve this force

Answer 7

Question 8

Newton’s first law

Answer 8

A body will remain at rest, or continue to move at a uniform velocity, unless acted upon by a resultant force

Question 9

What is inertia

Answer 9

a measure of how difficult it is to change the velocity of a body.

Question 10

How does mass effect inertia

Answer 10

greater the mass of a body, the greater its inertia…… the more difficult it is to change its velocity… the more difficult it is to accelerate the body.

Question 11

Describe and explain what happens to a person when they are standing on a bus that suddenly brakes.

Answer 11

Both the bus and person are moving at the same velocity before the bus brakes.

After braking, the bus comes to rest, but by Newton’s First Law, the person continues to move at the same velocity as no resultant force has yet acted on the person.

Thus, the person is seen to “jolt” abruptly forwards.

Question 12

Newtons 2nd law (definition)

Answer 12

The acceleration experienced by a body is directly proportional to the resultant force acting upon it, and in the same direction as

Question 13

Newton’s second law (formula)

Answer 13

F = ma

Question 14

What is acceleration

Answer 14

ACCELERATION IS THE RATE OF CHANGE OF VELOCITY OF A BODY

Question 15

Acceleration formula

Answer 15

a = ((𝐯−𝐮))/𝐭

Question 16

What is terminal velocity

Answer 16

The velocity at which a body falls through a medium, when the drag acting on the body is equal to its weight.

Question 17

Parachute velocity - Time Graph

Answer 17

Question 18

Explains what happens when a parachutist jumps out of a plane (6 marks)

Answer 18

• When parachutist jumps, the drag force acting is small so parachutist experiences large acceleration, due to the force of his weight
• As his speed increases, the drag force acting on him will increase so the resultant force on him will decrease and his acceleration will decrease
• ## Eventually the drag force will equal the weight. Acceleration is now zero and the speed is constant - this is known as Terminal Velocity.

Question 19

How to resolve a box on a slope force

Answer 19

Don’t understand this

Question 20

Calculate the size of the normal contact force of a block on a ramp if the weight of the block is 2N, and the angle between the weight and the component of weight that balances it is 30°.

Answer 20

I UNDERSTAND NOW

Question 21

Momentum equation

Answer 21

p = m x v

Momentum (Kgm/s) = mass x velocity

Question 22

Units of momentum

Answer 22

Kgm/s

Question 23

What is the law of conservation of momentum

Answer 23

The total momentum before an event is equal to thetotal momentum after the event.

Question 24

If a stationary body hits a moving body…

Answer 24

the two bodies will move off together.

Question 25

Work done equation

Answer 25

W = F x d

Question 26

A builder pushed a wheelbarrow of weight 200N up a slope(at constant velocity), a distance of 15m, and height 10m.

a) much work did she do against gravity?

b) If the total work done was 2500J,how much friction was acting?

Answer 26

a) Doing work against gravity, means opposing the weight, which only acts straight down…W = F x d = 200N x 10m = 2000J

B) (total work) = (work done against gravity) + (work done against friction)

=> (work done against friction) = (total work) – (work done against gravity)=> (work done against friction) = 2500J – 2000J = 500J

W = F x d=> F = W/d = 500J/15m = 33N (2 s.f.) of FRICTION

FRICTION = FORCE

Question 27

What is power (definition)

Answer 27

Power is the rate of energy transfer.

Question 28

What is power (equation)

Answer 28

P = E / t

Question 29

What is the unit of power

Answer 29

Watt

= 1 Watt is 1 Joule of energy transferred in 1 second.
= 1 kilowatt, kW is 1000 Joules of energy transferred in 1 second.