Two horizontal forces,

P and Q, are acting on a block that is placed on a table. We know that
P =(−1.10i + 4.25k) N
but the magnitude and direction of
Q are unknown. The block moves along the table. Assume there is no friction between the object and the table. Here the mass of the block is 4.10 kg.

a) What is Q when velocity is constant?

b)Determine the force
Q when the acceleration of the block is (−4.50i + 2.25k) m/s^2.
Express your answer in vector form.

c) Determine the force
Q when the acceleration of the block is (4.50i − 2.25k) m/s^2. Express your answer in vector form.

So far I know that a) is just
Q =(1.10i - 4.25k) N

2 answers

when velocity is constant, Q=-P
b)
Net force=ma
P+Q=ma
Q= ma-P
= 4.1((3.5i-2.25k)-( −1.10i + 4.25k)
you can do that.

c? same as b.
for b) and c), determine the force (Q) using the acceleration components and the components of (P) ... you have the mass of the block

f = m a ... by components