1.
· Shoes have friction so that we can walk and not slip easily.
· Frictions are used in erasers to remove pencil lead.
· Parachutes are made to resist air to prevent the user from death.

2a. Acceleration is defined as the gradual increase of speed irrespective of its direction of motion. It refers to the rate of change of velocity as a function of time.

A=v-u/t
It means that the object is increasing at the speed of 5m/s2

2bi.Decreasing (or)15m/s
Increasing (or) 30m/s
Increasing (or) 45m/s

ii. When the velocity is negative, the is actually slowing down. It is also known as deceleration. It can be represented that carthe deceleration of the car is at a constant speed of 5m/s.
The negative sign means the object is travelling at an opposite direction. The numerical value determines how fast or slow is the object moving.
It means the car is decreasing it’s speed at -5m/s (going through retardation). If the values is positive it means the car is accelerating at a 5m/s

iii. It remains constant because the question doesn’t say that the car accelerated from a point and when it decelerated. Unless they say the cars slows down at certain timings.
The car is moving at a speed of 5m/s but to an opposite direction.
The car is slowing down.

c. The velocity of the blade when going up is the same as when the blade is moving down because of the absence in air resistance, friction and gravitational force.
The speed will be different when raise because of the free fall.
d. The non-uniform value is due to air resistance, friction and gravitational force. Air-resistance and friction will enable David more time to escape whereas gravitational pull will decrease his time to escape.

3a. The difference is that David did not consider resistance and the reading for speed in his profile is constant. Whereas Harry considered resistance and the readings for speed is varied.
Profile A shows that the speed of the blade will increase whereas profile B shows that the blade will fall at a constant speed.

b. Harry. His graph shows a variable in speed due to resistance.
Profile A. This is because if it did not take resistive force into consideration, it would have be a 10m/s^2 acceleration per second.

c. No. It is not accurate because the profile does not show various resistance available when conducting the experiment.
or
Yes. The differences in the motions of the blade in the 2 profiles will be that one would fall slower than the other.

4a. ??
b. i. 0m/s
ii. 10m/s
iii. 10m/s
c. A line going upwards (slightly bent).
d. A straight line going upwards.
e. One shows that the velocity is increasing while the other shows that it is constant.

5a. 10+4=14km
b. 10-4= 6km (displacement) (or)14km
c. The car would be 4km away from the house
Negative displacement means travelling in an opposite direction
or
The car is 2km away from the house

6a. ??
b. One is a slightly curved line while the other is a straight line.

7a. 12 to 15s.
Because the line is at the negative portion of the graph.
or
8 seconds. this is because the car‘s displacement is decreasing

b. The object is accelerating at constant speed from 0-5s. From 5-8s the accelerating of the object is constant. From 8-10s the car is decelerating dramatically. At 10-12s the displacement occurs where the car is going the opposite direction.
or
From 0s to 5s, the car is moving is accelerating, 5s to 8s, moving at a constant speed, 8s to 10s, decreasing speed, 10s to 12s, constant speed again. Lastly, 12s to 15s, there is a change in direction