Hey Artillery, good to see you again.
Here are the solutions to your assignment questions:
1. Speed-time graph analysis
a) Find the speed V, if the deceleration in the first 3 seconds was 2m/s2.
Step 1: Deceleration is the negative of the gradient of the speed-time graph.
Deceleration=−changeintimechangeinspeed
2=−3−0V−24
Step 2: Solve for V.
2×3=−(V−24)
6=−V+24
V=24−6
V=18 m/s
b) Distance covered in the first 13 seconds.
Step 1: The distance is the area under the speed-time graph. This consists of a trapezium (from t=0 to t=3) and a rectangle (from t=3 to t=13).
Areaoftrapezium=21(u+v)h=21(24+18)×3
Areaoftrapezium=21(42)×3=21×3=63m
Step 2: Calculate the area of the rectangle.
Areaofrectangle=width×height=(13−3)×18
Areaofrectangle=10×18=180m
Step 3: Sum the areas to find the total distance.
Totaldistance=63+180=243 m
c) Value of t.
Step 1: The car decelerates at 3m/s2 from t=13 until it comes to rest (speed 0m/s). The initial speed for this segment is V=18m/s.
Acceleration=changeintimechangeinspeed
−3=t−130−18
Step 2: Solve for t.
−3(t−13)=−18
t−13=−3−18
t−13=6
t=13+6
t=19 s
d) Total distance for the whole journey.
Step 1: The total distance is the sum of the distance covered in the first 13 seconds (from part b) and the distance covered in the last segment (from t=13 to t=19).
Distanceinfirst13s=243m
Step 2: Calculate the distance in the last segment (area of a triangle).
Areaoftriangle=21×base×height=21×(19−13)×18
Areaoftriangle=21×6×18=3×18=54m
Step 3: Sum the distances.
Totaldistance=243+54=297 m
e) Average speed of the car.
Step 1: Average speed is calculated as total distance divided by total time.
Averagespeed=TotaltimeTotaldistance
Averagespeed=19s297m
Averagespeed=15.63 m/s (to 2 d.p.)
f) Speed of the car at 15 seconds.
Step 1: At t=15 seconds, the car is in the final deceleration phase, which starts at t=13 with a speed of 18m/s and a deceleration of 3m/s2.
Using the formula v=u+at′, where u=18m/s, a=−3m/s2, and t′=15−13=2s.
v=18+(−3)×2
v=18−6
v=12 m/s
2. If y=2x4+5, find dxdy.
Step 1: Differentiate each term with respect to x.
dxdy=dxd(2x4)+dxd(5)
Step 2: Apply the power rule for differentiation (dxd(axn)=anxn−1) and the rule for constants (dxd(c)=0).
dxdy=2×4x4−1+0
dxdy=8x3
3. Evaluate ∫02(3x2+2x)dx.
Step 1: Find the indefinite integral of the function.
∫(3x2+2x)dx=32+1x2+1+21+1x1+1+C
∫(3x2+2x)dx=33x3+22x2+C
∫(3x2+2x)dx=x3+x2+C
Step 2: Evaluate the definite integral using the limits of integration.
[x3+x2]02=(23+22)−(03+02)
=(8+4)−(0+0)
=12−0
=12
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