A window washer on a hanging platform cleans the outside of windows on a skyscraper. The washer hoists the platform up the side
of the building by pulling down on a rope that runs up over a pulley and then runs back down and connects to the top of the platform. The combined mass of the washer and the platform is 100kg, and the washer pulls on the rope with a force of 800N. What is the acceleration of the platform?
1 answer:
Answer:
Acceleration of the platform = - 1.8 m/s²
Explanation:
The net force acting on a body accelerates the body in the same direction as that in which the resultant is applied.
Writing the force balance for the setup,
ma = 800 - mg
100a = 800 - 100×9.8
100a = - 180
100a = - 180
a = - 1.8 m/s²
This means the body falls downwards.
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<u>Answer:</u>
a) Minimum speed must he drive off the horizontal ramp = 39.78 m/s
b) Minimum speed must he drive off the horizontal ramp with 7° above the horizontal = 23.93 m/s
<u>Explanation:</u>
a) The height of ramp = 1.5 meter
Horizontal distance he must clear = 22 meter
The car is having horizontal motion and vertical motion. In case of vertical motion the acceleration on the car is acceleration due to gravity.
We have equation of motion, , s is the displacement, u is the initial velocity, a is the acceleration and t is the time.
In case of vertical motion initial velocity = 0 m/s, acceleration = 9.8 , we need to calculate time when displacement = 1.5 meter.
So the car has to cover a distance of 22 meter in 2.119 seconds.
So minimum speed required = 22/0.553 = 39.78 m/s
Minimum speed must he drive off the horizontal ramp = 39.78 m/s
b) When the take of angle is 7⁰ the vertical speed of car is not zero = V sin 7 = 0.122 V
So the in case of vertical motion we have initial velocity = 0.122 V, S = -1.5 meter( below ramp), acceleration = -9.8
Substituting
In case of horizontal motion
Horizontal speed of car = V cos 7 = 0.993V
So it has to travel 22 meter in t seconds
0.993Vt = 22, Vt = 22.155 m
Substituting in the equation
We will get
Speed required = 22.155/0.926 = 23.93 m/s
Minimum speed must he drive off the horizontal ramp with 7° above the horizontal = 23.93 m/s