Gravity is the force that pulls you down.
(This is kind of a duh! question ... How do we know
which way is "down" ? We feel gravity, and we call
that the "down" direction.)
Magnetic force holds things to fridge doors.
Contact forces need to touch something in order to
exert their force.
Example: Gravity is NOT a contact force.
I don't know about "rubbing things away".
This might be a description of friction, but if so,
it's not a good one.
Buoyant force is what keeps floating things floating.
Air resistance slows things down when they move in air.
Answer:
Workdone = 600 Kilojoules
Explanation:
Given the following data:
Time = 8 seconds
Power = 75,000 Watts
Distance = 58 m
To find the work done;
Power can be defined as the energy required to do work per unit time.
Mathematically, it is given by the formula;
Thus, work done is given by the formula;
Workdone = power * time
Workdone = 75000 * 8
Workdone = 600,000 = 600 KJ
Answer:
a ) = 381.48 J
b )= 84.25 cm
Explanation:
Kinetic energy of the runner
= 1/2 m v²
= .5 x 66 x 3.4²
= 381.48 J
The final kinetic energy of the runner is zero .
Loss of mechanical energy
= 381.48 J
This loss in mechanical energy is due to action of frictional force .
b )
Let s be the distance of slide
deceleration due to frictional force
= μmg/m
.7 x 66 x 9.8 / 66
a = - 6.86 m s⁻¹
v² = u² - 2 a s
0 = 3.4² - 2x6.86 s
s = 3.4² / 2x6.86
= .8425 m
84.25 cm
Answer:
Explanation:
Average velocity in the 24 m interval is 24 / 4 = 6 m/s
Average velocity in the 64 m interval is 64 / 4 = 16 m/s
There is a 4 second interval between the two points where average velocity equals actual velocity
a = Δv/t = (vf - vi) / t = (16 - 6) / 4 = 2.5 m/s²
s = v₀t + ½at²
24 = v₀(4) + ½(2.5)4²
4v₀ = 24 - 20
v₀ = 1 m/s
Not asked for but the velocity at the end of the first segment and beginning of the second segment is 11 m/s and final velocity is 21 m/s