17 A motor is used to lift a load vertically upwards.The load has weight W.The motor produces useful power output P.The load is lifted at constant velocity v.Which expression gives the time taken for the motor to lift the load vertically upwards through adistance d ?A WdP B PWv C PWd D WPv18 A lamp is switched on for 2.0 hours. The power input to the lamp is 1.0 W. The energy given outby the lamp as light is 7.0  10 3 J.How much energy is converted to other forms by the lamp?A 120 J B 200 J C 3400 J D 7200 J19 An object of mass m is dropped onto the surface of two planets, X and Y, which have noatmosphere.The height from which the object is dropped and the change in gravitational potential energy ofthe object, for each planet, are given in the table.height / m change in gravitationalpotential energyplanet X 3 ∆Eplanet Y 4 4∆EThe acceleration of free fall near the surface of planet X is gX .What is the acceleration of free fall near the surface of planet Y?A X43 g B X34 g C 3gX D 4gX20 A known tensile force acts on a metal wire. The wire does not exceed its limit of proportionality.Which two measurements enable the strain of the wire to be calculated?A the unstretched length of the wire and the cross-sectional area of the wireB the unstretched length of the wire and the extension of the wireC the Young modulus of the metal and the extension of the wireD the Young modulus of the metal and the unstretched length of the wire

Sure, here are the answers to your questions:

17. The time taken for the motor to lift the load vertically upwards through a distance d can be calculated using the formula for power, which is work done per unit time. In this case, the work done is the weight of the load times the distance lifted (Wd). Since the load is lifted at a constant velocity, the power output is constant. Therefore, the time taken (t) is the work done divided by the power output. So, the correct answer is A (Wd/P).

18. The total energy input to the lamp is the power input times the time, which is 1.0 W * 2.0 hours = 7200 J. The energy given out by the lamp as light is 7.0 * 10^3 J. Therefore, the energy converted to other forms by the lamp is the total energy input minus the energy given out as light, which is 7200 J - 7.0 * 10^3 J = 200 J. So, the correct answer is B (200 J).

19. The change in gravitational potential energy is proportional to the height from which the object is dropped and the acceleration of free fall. Since the change in gravitational potential energy on planet Y is 4 times that on planet X, and the height is 4/3 times, the acceleration of free fall on planet Y is 3 times that on planet X. So, the correct answer is C (3gX).

20. Strain is defined as the extension per unit length. Therefore, to calculate the strain of the wire, we need to know the extension of the wire and the original (unstretched) length of the wire. So, the correct answer is B (the unstretched length of the wire and the extension of the wire).