GCSE Physics

Friday, 9 March 2012

Power is the rate of doing work. Power is measured in watts (W). An object has a higher power if it does more work in a certain time, or if it takes less time to do a certain amount of work.

Person	Force (N)	Distance moved (m)	Work done (J)
Alice	50	3	150
Bernard	10	10	100
Courtney	200	1	200
Dionne	500	0.3	150
Edward	75	2	150

3 Lowest power Bernard (10 W)

Alice (15 W)

Courtney (20 W)

Edward (25 W)

Dionne (30 W)

1 70 x 9.8 x 5 = 3430 J

2 3430/7 = 490 W

3 The work done on each flight of stairs is the same as the one before.

4 The time taken to climb each flight of stairs is longer than the one before.

5 (Exact figures may vary slightly depending on whether pupils calculate each time separately from work/power or calculate the increase from the previous time directly.)

Flight of stairs	Work done in climbing flight (J)	Power (W) (to 1 d.p.)	Time to climb flight (s) (to 1 d.p.)
1	3430	490.0	7.0
2	3430	465.5	7.4
3	3430	442.2	7.8
4	3430	420.1	8.2
5	3430	399.1	8.6
6	3430	379.2	9.0
7	3430	360.2	9.5
8	3430	342.2	10.0