Question

2. If you exert a force of 10.0 N to lift a box a distance of 0.9 m, how much work have you done?

0.1 J
9.0 J
10.9 J
90.0 J
3. The power of a machine measures
its rate of doing work.
its strength.
the force it produces.
the work it does.
4. If you exert a force of 700 N to walk 6 m up a flight of stairs in 6 s, how much power do you use?
19 W
25,200 W
700 W
4,200 W
5. A 750-W motor might also be rated as a
0.5-horsepower motor.
1-horsepower motor.
2-horsepower motor.
10-horsepower motor.

Answer 1

(2) The work done is, 9.0 J

(3) The power of a machine measures its rate of doing work.

(4) The power used, 700 W

(5) A 750-W motor might also be rated as a 1-horsepower motor.

Solution for part (2) :

Formula used :
`W=F* d`

where,

W = work done = ?

F = applied force = 10 N

d = displacement = 0.9 m

Now put all the given values in the above formula, we get the work done.

`W=(10N)* (0.9m)}=9J`

Therefore, the work done is, 9.0 J

Explanation for part (3) :

Power : it measures the rate of doing work by time.

Formula for power is,
`Power=(Work)/(time)`

Solution for part (4) :

Formula used :
`P=(W)/(t)=(F* d)/(t)`

where,

W = work done

F = applied force = 700 N

d = displacement = 6 m

t = time taken = 6 s

Now put all the given values in the above formula, we get the work done.

`P=(700N* 6m)/(6s)=700W`

Therefore, the power used, 700 W

Solution for part (5) :

As, 746 watt is equal to 1 horsepower

So, 750 watt is equal to
`(750)/(746)=1.005=1\text{ horsepower}`

Therefore, a 750-W motor might also be rated as a 1-horsepower motor.

Answer 2

force of 10.0 N

distance of 0.9 m
w=f*d
w=10*0.9
=9.0 j