Mohamed BOUCHAKOUR said:Homework Statement
A ball with a mass of 200g, is hanged on the roof of a bus with a rope (it's mass is negligible), when the bus starts moving, the rope makes an angle of 18°.
What's the acceleration of the bus?
Homework Equations
ΣF=m.a
The Attempt at a Solution
The first thing i thought of is air friction, but it related to speed not acceleration, and the ball is inside the bus, it would be negligible.
Nothing exept that came to my mind.
Yeah, but the only forces i can think of are gravity and rope.kuruman said:You're right, air resistance is not an issue because the air moves with the bus. How about drawing a free body diagram?
PeroK said:You can ignore the air resistance. Two questions:
What happens to something inside the bus that is attached to the bus?
What happens to something inside the bus that is not attached to the bus?
Mohamed BOUCHAKOUR said:If somthing is attached, it accelerate at the same rate as the bus.
Mohamed BOUCHAKOUR said:And if it's not (ignoring friction) it would roll back.
In a way yes(the 18° angle) , but then the rope prevents it from continuing,PeroK said:Is the ball in this case rolling back?
Mohamed BOUCHAKOUR said:In a way yes(the 18° angle) , but then the rope prevents it from continuing,
AcceleratingPeroK said:What does that mean in the ground frame?
What does someone outside the bus see happen to the ball? Is it rolling/stationary/accelerating?
Mohamed BOUCHAKOUR said:Accelerating
Still can't see it...PeroK said:So now you know all the forces on the ball. Or, at least, can calculate them.
Mohamed BOUCHAKOUR said:Still can't see it...
I think I've got it, thanks for the help ✌✌PeroK said:Have a think and draw a free-body diagram.
The formula for finding acceleration from the angle made by a hanged ball is a = g * tan(theta), where a is the acceleration, g is the acceleration due to gravity (9.8 m/s^2), and theta is the angle made by the hanged ball.
The angle made by a hanged ball can be measured using a protractor or a smartphone app with an inclinometer feature. Place the protractor or the smartphone on the same plane as the string or rope holding the ball, and measure the angle between the string and the vertical line.
No, the angle made by a hanged ball cannot be negative as it is measured from the vertical line.
Finding acceleration from the angle made by a hanged ball can help in determining the acceleration due to gravity and can also be used in experiments to study the motion of objects under the influence of gravity.
Yes, there are factors that can affect the accuracy of finding acceleration from the angle made by a hanged ball. These include air resistance, friction, and the precision of the angle measurement. It is important to minimize these factors to obtain an accurate result.