Answer:
Air resistance
Answer B is correct
Explanation:
The friction that occurs when air pushes against a moving object causing it to negatively accelerate is called as air resistance.
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Answer:
The minimum speed when she leave the ground is 6.10 m/s.
Explanation:
Given that,
Horizontal velocity = 1.4 m/s
Height = 1.8 m
We need to calculate the minimum speed must she leave the ground
Using conservation of energy
Put the value into the formula
Hence, The minimum speed when she leave the ground is 6.10 m/s.
Answer:
78 km/h
Explanation:
If I normally drive a 12 hour trip at an average speed of 100 km/h, my destination has a total distance of:
- 100 km/h · 12 h = 1,200 km
Today, I drive the first 2/3 of the distance at 116 km/h. Let's first calculate what 2/3 of the normal distance is.
I've driven 800 km already. I need to drive 400 km more to reach my final destination. I need to figure out my average speed during this last 1/3 of the distance.
To do this, I first need to calculate how much time I spent driving 116 km/h for the past 800 km.
- 116 km/1 h = 800 km/? h
- 800 = 116 · ?
- ? = 800/116
- ? = 6.89655172
I spent 6.89655172 hours driving during the first 2/3 of the distance.
Now, I need to subtract this value from 12 hours to find the remaining time I have left.
- 12 h - 6.89655172 h = 5.10344828 h
Using this remaining time and my remaining distance, I can calculate my average speed.
- ? km/1 hr = 400 km/5.10344828 h
- 5.10344828 · ? = 400
- ? = 400/5.10344828
- ? = 78.3783783148
My average speed during the last third of the distance is around 78 km/h.
Newton’s second law gives us the relationship of force F,
mass m and acceleration a. The formula is given as:
<span>F = m a -->
1</span>
However we also know that the relationship of mass m,
density ρ, and volume V is:
<span>m = V ρ -->
2</span>
Therefore substituting equation 2 to equation 1:
F = ρ V a = ρ V g
where a is acceleration due to gravity, ρ is density of
water and V is the volume of the casting, therefore:
F = (1x10^-3 kg/cm^3) (4840 cm^3) (9.8 m/s^2)
F = 47.432 kg m/s^2
F = 47.432 N
Going back to equation 1:
47.432 N = m (9.8 m/s^2)
m = 4.84 kg
<span>Hence the weight of the final casting is 4.84 kg</span>
<span>if we take ball then the Kinetic Energy of the ball is ½mV²
as it rolls up the slope, the Kinetic Energy is converted to potential energy, PE = mgh.
mgh = ½mV²
h = V²/2g</span>
