Question 5
The first column in
the table gives four examples of work being done. The second column gives more
detail of the action.
Which row is not correct?
Note: The question is the same in both papers,
except that in the November 2011 one, ‘gravity’ is used instead of ‘gravitational
field’ for option A.
Reference: Past Exam Paper – November 2011 Paper 13 Q16 + June 2017 Paper
13 Q14
Solution:
Answer:
A.
Work Done = Force × Distance moved in direction of the
force
Case
A: a girl dives from a diving board
into a swimming pool
Direction of force
(gravitational) = downwards
Direction of motion =
horizontal
Row A is incorrect. So,
the solution to the question is A.
Case
B: a man pushes a car along a level road
Both the frictional force
and the motion are horizontal.
Case
C: an electron is accelerated towards a positively charged
plate
Direction of force
(electric force) = towards positively charged plate
Direction of motion:
electron is moving (accelerating) towards the positive charge
Case
D: a piston is pushed outwards as a gas expands
Direction of force = on piston
(the atmosphere exerts a force on the surface of the piston)
Direction of motion =
piston moves outwards
For Question 5 right, I thought the direction of electric force is from positively charged plate to negatively charged plate?
ReplyDeletethe direction of the electric FIELD (not necessarily force) is from +ve to -ve. But remember that the direction of the electric field is that direction of the force on a positive charge.
DeleteHere, we are considering an electron, which is negative. An electron will be attracted to the positive plate. So, the direction of the FORCE is towards the positive plate.