+33616 4) Ball rolling down hill.
A ball rolling down a hill, in the absence of any significant friction or drag, is going to speed up, so the answer will be one with speed increasing.
The acceleration will result from the component of the gravitational force tangential to the surface of the hill. Because the slope is decreasing as we move towards the bottom of the hill, this component is decreasing (when the ball is on the flat at the bottom of the hill, the tangential component of acceleration is zero, of course).
2) d: Constant velocity must mean zero acceleration, so one cannot have constant velocity with changing (i.e. non-zero) acceleration.
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+33616 (a). Because the plane is rising at constant velocity (not accelerating) the net vertical force must be zero. That is the upward force of 8000*sin(65) must equal the weight of the plane.
(b). Forward acceleration is obtained from mass*acceleration = 8000*cos(65°). The mass of the plane is its weight divided by g (acceleration of gravity).
(c). There are two forces acting on the plane: The 8000N in the direction shown and its weight acting vertically down. From (a) you know the net vertical force is zero, so can you figure out what is left?
+1832 these are my answers :-
1 - c
2 - d
3 - a
4 - d
5 - d
are they correct ?
+33616 No, on second thoughts, I agree with your answer (I looked at this too quickly!)
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+118609 Hi Alan and 315,
I am also trying to learn from these questions.
Question 2
I know that b and c are not possible but I am confused by a and d
Alan ( or 315) could you please discuss a and d ?
I am also struggling with the NEW question 4.
+33616 4) Ball rolling down hill.
A ball rolling down a hill, in the absence of any significant friction or drag, is going to speed up, so the answer will be one with speed increasing.
The acceleration will result from the component of the gravitational force tangential to the surface of the hill. Because the slope is decreasing as we move towards the bottom of the hill, this component is decreasing (when the ball is on the flat at the bottom of the hill, the tangential component of acceleration is zero, of course).
2) d: Constant velocity must mean zero acceleration, so one cannot have constant velocity with changing (i.e. non-zero) acceleration.
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+118609 Thanks Alan,
In Q2 it was a and d that confused me (not b and d)
SO I would still like you to discuss a please.
The question was
Which is NOT possible.
a) A body travels with a constant acceleration and a time varying velocity,
d) A body travels with a constant velocity and a time varying accelteration.
The words 'time varying ' confuse me
BUT consider d
Say the body was travelling in a circular motion. Then the velocity could be contant and the acceleration would not be 0.
If it was travelling in an curved path, couldn't it have a constant velocity and a time varying acceleration?
+33616 Sorry Melody, in my last reply I confused part of question 1 with question 2.
As far as question 2d is concerned, if the body is travelling in a circle the velocity is changing (though the speed might not be).
2a) Any acceleration will change the velocity, so 2a) is possible.
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