A credit card is set on top of a plastic tray and the tray is slowly accelerated across a table toward a waitress, taking the credit card with it. The patron of the restaurant pushing the tray does not touch the credit card. What type of force causes the credit card to accelerate?

What does si stand for,when referring to a system of measurement

Ahorizontal force of 400.0 n is required to pull a 1760 n truck across the floor at a constant speed. find the coefficient of sliding friction.

Refrigerant-134a flows through a carnot heat pump cycle at 0.5 kg/s. it is known that the maximum absolute temperature in the cycle is 1.1 times the minimum absolute temperature, and the net power input to the cycle is 2.5 kw. if the refrigerant changes from a saturated vapor to a saturated liquid during the heat rejection process, determine the maximum magnitude of the enthalpy of vaporization for this process in kj/kg (with 3 significant figures).