# Kinematics and Forces Problem Set

1) Please answer T or F and tell why true or false.

a) A body can be accelerating even when it is not moving.

b) The velocity of an accelerated body changes with time.

c) Motion and acceleration are not the same quantity

d) The words motion and acceleration can be used interchangeably.

e) The acceleration of a body with zero speed is zero.

2) A car traveling at 61km/h hits a bridge abutment. A passenger in the car moves forward a distance of 63cm (with respect to the road) while being brought to rest by an inflated air bag. What magnitude of force (assumed constant) acts on the passenger's upper torso, which has a mass of 49kg?

3) A 30.3kg girl and a 55.8kg boy are on the surface of a frozen lake, 13.0m apart. Using a rope, the girl exerts a horizontal 4.35N force on the boy, pulling him towards her. Calculate the magnitude of the girl's acceleration.

4) Three forces in the x-y plane act on a 5.8kg mass: 17.1 Ndirected at 11 degrees, 8 N directed at 140 degrees, and 4.4N directed at 197 degrees. All angles are measured from the positive x axis, with positive angles in the CCW direction.

a) Calculate the magnitude of the acceleration.

b) Calculate the direction of the resultant force using the same sign convention as above in degrees.

https://brainmass.com/physics/acceleration/kinematics-forces-problem-set-33271

#### Solution Preview

Solution:

1)

1) F, since it is acceleration, that means the velocity must change, it must move

2) T, V=V0+a*t

3) T, from the definition

4) F, definition

5) ...

#### Solution Summary

The solution includes True/False answers and calculations for (2) through (4).