P10 - Forces and Motion

Question 1

What is Newton’s First Law of Motion

Answer 1

If the resultant force on an object is 0, then the object will either remain stationary or continue at a constant velocity

Question 2

What is Newtons Second Law of motion

Answer 2

The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object

Question 3

Equation for Newtons Second Law

Answer 3

F = ma
Force = mass x acceleration

Question 4

What is the inertial mass

Answer 4

A measure of how difficult it is to change the velocity of an object
A large inertial mass means a large force is needed to produce a given acceleration

Question 5

What is Newtons Third Law of Motion

Answer 5

Whenever two forces interact, the forces they exert on each other are equal (im magnitude) and opposite (in direction)

Question 6

What forces act on a skydiver jumping out of a plane

Answer 6

1. Initially, the only force is weight due to gravity
2. The diver accelerates towards the ground
3. They experience air resistance
4. As the velocity increases, so does the air resistance
5. Soon, they are balanced, the velocity stays constant (TERMINAL VELOCITY)

Question 7

What is the total stopping distance

Answer 7

The total distance from when the driver thinks to stop to the position where the car stops
It can be divided into thinking distacne and breaking distance

Question 8

What is the thinking distance and factors that can affect it

Answer 8

• The distance travelled by the car during the reaction time
• Tiredness, alcohol, certain drugs and distraction can all increase the reaction time

Question 9

What is the the stopping distance and factors that can affect it

Answer 9

• The distacne from applying the brake to the car stopping
• Wet or icy conditions, how worn the tyres are and how worn the brakes are all affect braking distance

Question 10

Equation for momentum do moving, stationary or both have it

Answer 10

• Only moving objects have momentum
• p = mv
• Momentum (kg m/s) = mass x velocity

Question 11

What is the conservation of momentum

Answer 11

In a closed system, the total momentum before an event is equal to the total momentum after an event

Question 12

How is an airbag a good safety feature

Answer 12

• When you crash, the change in momentum of a car is rapid which can be fatal
• However, airbags increase the impact time after the crash that the change in momentum has to act
• Thius reduces the force you experience as force = change in momentum/time

Question 13

What is inertia

Answer 13

The tendency of an object to remain in a steady state e.g. resting or uniform velocity

Question 14

typical values for walking, running and cycling

Answer 14

• Walking ≈ 1.5m/s
• Running ≈ 3m/s
• Cycling ≈ 6m/s