Energy and Power Physics Questions?
1. If you push against a wall, are you doing any work on the wall?
? a. Yes, the effort tires you out.
? b. Yes, you are applying force to the wall.
? c. No, the wall doesn't move.
? d. No, you don't move.
2. A person does 45 J of work by dragging a 22 kg box 3.7 m across the floor. How much force does this require?
? a. 0.55 N
? b. 2.04 N
? c. 12.2 N
? d. 58 N
Questions 4 and 5
A 0.32 kg ball is thrown with a speed of 11.5 m/s.
4. How much kinetic energy does the ball have?
? a. 21.2 J
? b. 42.3 J
? c. 1.84 J
? d. 35.9 J
5. How much work would be needed to stop the ball?
? a. 1.84 J
? b. 21.2 J
? c. 35.9 J
? d. 42.3 J
Can you please help me? i totally forgot how to do them!?
1) C Work = Force * Distance..the wall doesn't move, so distance = 0 so there is no work
2) C W = F*d ; F = W/d = 45/3.7 = 12.2N
4) A E = .5mv2 = 21.2 J
5) B Stopping a moving object is the opposite of getting it to move, therefore it would be the same as number 4) 21.2 J
1: C because work is only done when a force is applied and it moves a certain distance in the same direction
2: A because: Work Done = Force x Distance
Force = mass x R
F = 22R
45 = 22R x 3.7
R = 0.5528...
KE = 1/2 mv^2
KE = 1/2 x 0.32 x (11.5^2)
KE = 21.16
KE = 21.2 (3sf)
WD = change in kinetic energy
WD = 1/2mv^2 - 1/2mu^2
v = 0 when ball stops, u = 11.5
WD = 0 - (1/2 x 0.32 x 11.5^2)
WD = 21.2