Physics
For each of the following scenarios, state whether the work done by gravity is positive, negative, or zero.
(a) a person walks on a levelled road.
(b) a person climbs a ladder.
(c) a car in neutral gear is coming down the slope.
Work, Energy & Power
1 Like
Answer
(a) Zero because when a person walks on a levelled, no work is done against the force of gravity as the displacement of the person is normal to the direction of force of gravity which is vertically downwards.
(b) Negative because when a person climbs a ladder (upward), the displacement covered by the person is opposite to the direction of force of gravity (downwards), so the work done on the person by the force of gravity is negative.
(c) Positive because when a car in neutral gear is coming down the slope, the direction of displacement covered by it is parallel to the direction of force of gravity (downwards), so the work done on the car by the force of gravity is positive.
Answered By
1 Like
Related Questions
O is a luminescent particle trapped inside a glass block. A student traces the path of rays coming out of it and reflecting over a plane mirror as shown in the diagram below.
Complete the table, using the labels from the figure. The first label is done for you.
S. No. Description Label a. an angle of reflection on the mirror a b. a partially reflected ray in the glass slab c. a critical angle d. a refracted ray e. an angle of refraction of the ray R A metal rod AB of length 80 cm is balanced at 45 cm from the end A with 100 gf weights suspended from the two ends.
(a) If this rod is cut at the centre C, then compare the weight of AC to the weight of BC.
(b) Give a reason for your answer in (a)
The figure below shows a simple pendulum of mass 200 g. It is displaced from the mean position A to the extreme position B. The potential energy at the position A is zero. At the position B the pendulum bob is raised by 5 m.
(a) What is the potential energy of the pendulum at the position В?
(b) What is the total mechanical energy at point C?
(c) What is the speed of the bob at the position A when released from B?
(Take g = 10 ms-2 and given that there is no loss of energy.)
A block and tackle system of pulleys has velocity ratio 4.
(a) Draw a labelled diagram of the system indicating clearly, the direction of the load and effort.
(b) Calculate the potential energy of the load 100 kgf lifted by this pulley to a height 5 m. (g = 10 ms-2)