Advertisements
Advertisements
Question
A force of 1 kgf displaces a body by a distance of 10 cm
(i) in direction of force,
(ii) normal to the force
(iii) at an angle of 60° to the direction of the force.
Calculate the amount of work done in each case. (Take: g = 9.8 ms−2 )
Advertisements
Solution
Given : F = 1 kgf = 1 × g Newton
(i) When displacement is in direction of force.
θ = 0°, cos 0° = 1
W = F × d = 9.8 × 0.1 = 0.98 J.
(ii) When displacement is normal to the force
θ = 90°, cos 90° = 0, i.e.,W = 0.
(iii) When displacement is at an angle of 60° to the direction of force
θ = 60° or, cos 60° =`1/2`
W = F . d cos θ = `9.8xx0.1xx1/2` = 0.49 J.
RELATED QUESTIONS
A stone of mass m is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions
1) Is the stone moving with a uniform or variable speed?
2) Is the stone moving with a uniform acceleration? In which direction does the acceleration act?
3) What kind of force acts on the hand and state its direction?
A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road.
Who does more work against the force of gravity and why?
A body is moved in a direction opposite to the direction of force acting on it. State whether the work is done by the force or work is done against the force
A body, when acted upon by a force of 10 kgf, gets displaced by 0.5 m. Calculate the work done by the force, when the displacement is (i) in the direction of force, (ii) at an angle of 60° with the force, and (iii) normal to the force. (g = 10 N kg-1)
State the principle of moments.
What do you mean by a centrifugal force?
It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B of same mass does the same in 15 s. Compare the power developed by the persons A and B.
A man raises a box of mass 50 kg to a height of 2 m in 20s, while another man raises the same box to the same height in 50s. Calculated:
- the work done, and
- the power developed by each man. Take g = 10 N kg-1.
In the following case write yes, if the work is being done and no if no work is being done.
A man trying to push a wall.
