Quiz about Work, Energy and Power (MCQ Only)

Question 1

A rope is used to apply a force F to a box as shown. The box is pulled a distance $$\Delta x$$ along a horizontal surface.

Which of the following could be used to determine the work done on the box?

Accepted Answer

$$F\Delta xCos heta$$

Answer

$$F\Delta xSin heta$$

Answer

$$\frac{F\Delta x}{Sin heta}$$

Answer

$$\frac{F\Delta x}{Cos heta}$$

Question 2

A power station provides electrical power at a mean rate of 3500 MW.

Which of the following gives the best estimate of the energy provided to consumers over a period of a year?

$$1\ year\ =\ 3.2 imes10^7s$$

(Hint:3500 MW=3.5 x 10⁹W)

Accepted Answer

$$1 imes10^{17}J$$

Answer

$$1 imes10^6J$$

Answer

$$1 imes10^{11}J$$

Answer

$$1 imes10^{13}J$$

Question 3

An object of mass m is moved from point A on the ground, to point B on a bench of height h as shown in the diagram.

Which of the following is a correct expression for the work done on the object?

Accepted Answer

$$mgh$$

Answer

$$\frac{mgh}{\sin heta}$$

Answer

$$\frac{mgh}{\cos heta}$$

Answer

$$mgh\sin heta$$

Question 4

An object of weight 7 N is raised from a height of 2 m to a height of 8 m. The change in gravitational potential energy is

Accepted Answer

$$42J$$

Answer

$$56J$$

Answer

$$412J$$

Answer

$$549J$$

Question 5

A cyclist travels up a slope through a vertical height h in a time t. The mass of the cyclist and his bike is m.

The average power of the cyclist is

Accepted Answer

$$\frac{mgh}{t}$$

Answer

$$\frac{m^2gh}{t}$$

Answer

$$mgh imes t$$

Answer

$$\frac{mgh}{t^2}$$

Question 6

A motor is used to lift an object as shown. The object is raised through a vertical height of 75 cm at a constant speed of 0.40 m s^-1with 0.25kg.

Which of the following gives the rate of increase of potential energy of the object in watts?

Accepted Answer

$$0.25 imes9.8 imes0.4$$

Answer

$$0.25 imes0.75$$

Answer

$$0.25 imes9.8 imes0.75$$

Answer

$$0.5 imes0.25 imes\left(0.4 ight)^2$$

Question 7

An object of mass m is moved from the bottom to the top of a slope. The vertical height of the slope is y.

The horizontal distance between the bottom and top of the slope is x.

Which of the following gives the gain of gravitational potential energy of the object as it moves from the bottom to the top of the slope?

Accepted Answer

mgy

Answer

mxy

Answer

mgx

Answer

my

Question 8

The velocity v of a non-relativistic particle can be expressed in terms of combinations of the following quantities: kinetic energy E_k, momentum p and mass m.

Which of the following expressions is correct?

Accepted Answer

$$v=\sqrt[]{\frac{2E_k}{m}}$$

Answer

$$v=\frac{p^2}{m}$$

Answer

$$v=\frac{E_k}{2p}$$

Answer

$$v=\frac{2E_k}{pm}$$

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