F.4 physics Force

2013-10-24 4:28 am

1. When 2kg trolley is given a push, it moves down an inclined plane of slope 10° with uniform velocity. What is the frictional force on the trolley?

2. A 30kg crate is pushed up a smooth ramp as shown.
a) Find the force F along the ramp required to move the crate at a constant speed.
b) What is the normal reaction R acting on the crate?

picture for question 2:
http://i1186.photobucket.com/albums/z369/kk3796797/IMG_4495_zps0f2d68f6.jpg

因為是想明白如何做，
所以希望能用中文解答，謝謝

回答 (1)

天同

2013-10-24 6:49 am

✔ 最佳答案

1. The downward weight component parallel to the plane
= 2g.sin(10) N = 3.473 N
where g is the acceleration due to gravity, taken to be 10 m/s^2

Because the trolley moves in uniform speed, it is subjected to no net force. Hence, the frictional force acting on the trolley is 3.473 N

2. (a) The downward weight component parallel to the plane
= 30g.sin(30) N = 150 N
Because the crate moves in constant speed, the applied force F = 150 N

(b) The normal reaction R
= 30g.cos(30) N
= 260 N

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