In each of the following cases identify all objects in the surroundings that exert forces on the system. You hit a baseball with a bat. Choose the baseball as the system. At the instant of contact with the bat, what objects should be included in the surroundings (what objects exert forces on the ball)?

The particle p starts from rest at point a at time t = 0 and changes its speed thereafter at a constant rate of 2.8g as it follows the horizontal path shown. determine the magnitude and direction of its total acceleration (a) just before point b, (b) just after point b, and (c) as it passes point c. state your directions relative to the x-axis shown (ccw positive) and choose the angle with the smallest magnitude.