Which of the following can cause an object to accelerate

Truck traveling west on the highway experiences an acceleration to the east. what could be the cause of this acceleration

Hey student studies gravity using objects that have the same mass which two objects have the greatest gravitational force acting between them a. 100kg 1.0m 100kg b. 100kg 2.0m 100kg c. 100kg 2.0m 100kg big d. 100kg big 3.0m 100kg big

Photons with the highest energy have the longest period