Answer:
Final angular velocity is 35rpm
Explanation:
Angular velocity is given by the equation:
I1w1i + I2w2i = I1w1f -I2w2f
But the two disks are identical, so Ii =I2
wf can be calculated using
wf = w1i - w2i/2
Given: w1i =50rpm w2i= 30rpm
wf= (50 + 20) / 2
wf= 70/2 = 35rpm


Now


- Lower mass=Higher acceleration
- Lower Force=Lower Acceleration
Option B has lowest mass and highest force hence its correct
Answer:
Driver hits the dog
Explanation:
From kinematics equation
and making a the subject

F=ma=800*-4=-3200 N
The driver is required to apply a force of 3200 N to effectively not hit the dog. However, when the driver applies 2000 N, this is less the required force by 1200 N hence the driver hits the dog.